From 157054c97eb9f4b263c5740515639955624a11af Mon Sep 17 00:00:00 2001
From: Matthias Schmidt <gravatronics@live.com>
Date: Sat, 21 May 2016 13:49:07 +0200
Subject: [PATCH] Use class constant

---
 .../acp/action/InstallPackageAction.class.php |  3 +-
 .../action/UninstallPackageAction.class.php   |  3 +-
 .../acp/action/WorkerProxyAction.class.php    |  5 +-
 .../acp/form/AbstractOptionListForm.class.php |  3 +-
 .../lib/acp/form/UserOptionListForm.class.php |  3 +-
 .../acp/page/ACPSessionLogListPage.class.php  |  3 +-
 .../lib/acp/page/ACPSessionLogPage.class.php  |  3 +-
 .../files/lib/acp/page/AdListPage.class.php   |  3 +-
 .../lib/acp/page/AttachmentListPage.class.php |  3 +-
 .../lib/acp/page/BBCodeListPage.class.php     |  3 +-
 .../BBCodeMediaProviderListPage.class.php     |  3 +-
 .../files/lib/acp/page/BoxListPage.class.php  |  3 +-
 .../page/CaptchaQuestionListPage.class.php    |  3 +-
 .../lib/acp/page/CronjobListPage.class.php    |  3 +-
 .../lib/acp/page/CronjobLogListPage.class.php |  3 +-
 .../lib/acp/page/LabelGroupListPage.class.php |  3 +-
 .../lib/acp/page/LanguageListPage.class.php   |  3 +-
 .../files/lib/acp/page/MenuListPage.class.php |  3 +-
 .../lib/acp/page/NoticeListPage.class.php     |  3 +-
 .../lib/acp/page/PackageListPage.class.php    |  3 +-
 .../PackageUpdateServerListPage.class.php     |  3 +-
 .../files/lib/acp/page/PageListPage.class.php |  3 +-
 .../page/PaidSubscriptionListPage.class.php   |  3 +-
 ...bscriptionTransactionLogListPage.class.php |  3 +-
 .../PaidSubscriptionUserListPage.class.php    |  3 +-
 .../lib/acp/page/SmileyListPage.class.php     |  3 +-
 .../lib/acp/page/StyleListPage.class.php      |  3 +-
 .../files/lib/acp/page/TagListPage.class.php  |  3 +-
 .../acp/page/TemplateGroupListPage.class.php  |  3 +-
 .../lib/acp/page/TemplateListPage.class.php   |  3 +-
 ...serAuthenticationFailureListPage.class.php |  3 +-
 .../UserGroupAssignmentListPage.class.php     |  3 +-
 .../lib/acp/page/UserGroupListPage.class.php  |  3 +-
 .../page/UserOptionCategoryListPage.class.php |  3 +-
 .../lib/acp/page/UserOptionListPage.class.php |  3 +-
 .../lib/acp/page/UserRankListPage.class.php   |  3 +-
 .../lib/action/AJAXProxyAction.class.php      |  5 +-
 .../AbstractDatabaseObjectAction.class.php    |  2 +-
 .../lib/data/DatabaseObjectList.class.php     |  4 +-
 .../data/ProcessibleDatabaseObject.class.php  |  7 +--
 .../data/acl/option/ACLOptionAction.class.php |  2 +-
 .../ACLOptionCategoryAction.class.php         |  2 +-
 .../acp/menu/item/ACPMenuItemAction.class.php |  2 +-
 .../log/ACPSessionAccessLogAction.class.php   |  2 +-
 .../session/log/ACPSessionLogAction.class.php |  2 +-
 .../acp/template/ACPTemplateAction.class.php  |  2 +-
 .../lib/data/bbcode/BBCodeAction.class.php    |  2 +-
 .../attribute/BBCodeAttributeAction.class.php |  2 +-
 .../BBCodeMediaProviderAction.class.php       |  2 +-
 .../data/category/CategoryNodeTree.class.php  |  2 +-
 .../action/ClipboardActionAction.class.php    |  2 +-
 .../response/CommentResponseAction.class.php  |  2 +-
 .../core/object/CoreObjectAction.class.php    |  2 +-
 .../lib/data/cronjob/CronjobAction.class.php  |  2 +-
 .../lib/data/cronjob/CronjobEditor.class.php  |  3 +-
 .../cronjob/log/CronjobLogAction.class.php    |  2 +-
 .../entry/EditHistoryEntryAction.class.php    |  2 +-
 .../listener/EventListenerAction.class.php    |  2 +-
 .../label/group/LabelGroupAction.class.php    |  2 +-
 .../data/language/LanguageAction.class.php    |  2 +-
 .../category/LanguageCategoryAction.class.php |  2 +-
 .../item/LanguageItemAction.class.php         |  2 +-
 .../files/lib/data/like/LikeAction.class.php  |  2 +-
 .../queue/ModerationQueueAction.class.php     |  2 +-
 .../object/type/ObjectTypeAction.class.php    |  2 +-
 .../ObjectTypeDefinitionAction.class.php      |  2 +-
 .../lib/data/option/OptionAction.class.php    |  2 +-
 .../category/OptionCategoryAction.class.php   |  2 +-
 .../lib/data/package/PackageAction.class.php  |  2 +-
 .../PackageInstallationPluginAction.class.php |  2 +-
 .../PackageInstallationQueueAction.class.php  |  2 +-
 .../update/PackageUpdateAction.class.php      | 15 +++---
 .../PackageUpdateServerAction.class.php       |  2 +-
 .../PackageUpdateVersionAction.class.php      |  2 +-
 .../files/lib/data/poll/PollAction.class.php  |  2 +-
 .../poll/option/PollOptionAction.class.php    |  2 +-
 .../lib/data/search/SearchAction.class.php    |  2 +-
 .../keyword/SearchKeywordAction.class.php     |  2 +-
 .../lib/data/session/SessionAction.class.php  |  2 +-
 .../files/lib/data/sitemap/Sitemap.class.php  |  5 +-
 .../lib/data/smiley/SmileyAction.class.php    |  2 +-
 .../category/SmileyCategoryAction.class.php   |  3 +-
 .../lib/data/spider/SpiderAction.class.php    |  2 +-
 .../data/stat/daily/StatDailyAction.class.php |  2 +-
 .../lib/data/style/StyleAction.class.php      |  2 +-
 .../lib/data/style/StyleEditor.class.php      |  3 +-
 .../variable/StyleVariableAction.class.php    |  2 +-
 .../files/lib/data/tag/TagAction.class.php    |  2 +-
 .../data/template/TemplateAction.class.php    |  2 +-
 .../lib/data/template/TemplateList.class.php  |  2 +-
 .../group/TemplateGroupAction.class.php       |  2 +-
 .../listener/TemplateListenerAction.class.php |  2 +-
 .../user/follow/UserFollowingAction.class.php |  2 +-
 .../data/user/group/UserGroupAction.class.php |  2 +-
 .../option/UserGroupOptionAction.class.php    |  2 +-
 .../UserGroupOptionCategoryAction.class.php   |  2 +-
 .../ignore/ViewableUserIgnoreList.class.php   |  8 +--
 .../user/menu/item/UserMenuItem.class.php     |  3 +-
 .../event/UserNotificationEvent.class.php     |  3 +-
 .../user/option/UserOptionAction.class.php    |  2 +-
 .../UserOptionCategoryAction.class.php        |  2 +-
 .../menu/item/UserProfileMenuItem.class.php   |  4 +-
 .../files/lib/page/FollowingPage.class.php    |  3 +-
 .../files/lib/page/IgnoredUsersPage.class.php |  3 +-
 .../files/lib/page/MembersListPage.class.php  |  3 +-
 .../lib/page/ModerationListPage.class.php     |  3 +-
 .../files/lib/page/MultipleLinkPage.class.php |  5 +-
 .../files/lib/page/SearchResultPage.class.php |  2 +-
 .../install/files/lib/system/CLIWCF.class.php |  4 +-
 .../install/files/lib/system/WCF.class.php    | 11 ++--
 .../files/lib/system/WCFSetup.class.php       |  5 +-
 .../application/AbstractApplication.class.php |  3 +-
 .../BackgroundQueueHandler.class.php          |  2 +-
 .../lib/system/bbcode/CodeBBCode.class.php    | 50 ++++++++++++-------
 .../builder/ACPMenuCacheBuilder.class.php     |  3 +-
 .../EventListenerCacheBuilder.class.php       |  3 +-
 .../builder/OptionCacheBuilder.class.php      |  3 +-
 .../builder/SmileyCacheBuilder.class.php      |  3 +-
 .../UserGroupOptionCacheBuilder.class.php     |  3 +-
 .../UserGroupPermissionCacheBuilder.class.php |  4 +-
 .../builder/UserMenuCacheBuilder.class.php    |  3 +-
 .../builder/UserOptionCacheBuilder.class.php  |  3 +-
 .../builder/UserStatsCacheBuilder.class.php   |  3 +-
 .../cli/command/WorkerCLICommand.class.php    |  5 +-
 .../clipboard/ClipboardHandler.class.php      |  5 +-
 .../action/TagClipboardAction.class.php       |  3 +-
 .../action/UserClipboardAction.class.php      |  3 +-
 .../UserContentClipboardAction.class.php      |  3 +-
 .../system/cronjob/CronjobScheduler.class.php |  4 +-
 .../lib/system/database/Database.class.php    |  5 +-
 .../system/database/MySQLDatabase.class.php   |  3 +-
 .../database/PostgreSQLDatabase.class.php     |  3 +-
 .../lib/system/event/EventHandler.class.php   | 12 ++---
 .../MultipleSelectionFormElement.class.php    |  3 +-
 .../lib/system/image/ImageHandler.class.php   |  6 ++-
 .../AbstractAttachmentImporter.class.php      |  2 +-
 .../AbstractCategoryImporter.class.php        |  3 +-
 .../AbstractCommentImporter.class.php         |  3 +-
 .../AbstractCommentResponseImporter.class.php |  3 +-
 .../importer/AbstractLikeImporter.class.php   |  3 +-
 .../importer/AbstractPollImporter.class.php   |  3 +-
 .../AbstractPollOptionImporter.class.php      |  3 +-
 .../AbstractWatchedObjectImporter.class.php   |  3 +-
 .../importer/LabelGroupImporter.class.php     |  3 +-
 .../system/importer/LabelImporter.class.php   |  3 +-
 .../system/importer/SmileyImporter.class.php  |  4 +-
 .../importer/UserAvatarImporter.class.php     |  3 +-
 .../importer/UserFollowerImporter.class.php   |  3 +-
 .../importer/UserGroupImporter.class.php      |  2 +-
 .../system/importer/UserImporter.class.php    |  2 +-
 .../importer/UserOptionImporter.class.php     |  3 +-
 .../importer/UserRankImporter.class.php       |  3 +-
 .../lib/system/label/LabelHandler.class.php   |  3 +-
 .../AbstractLabelObjectHandler.class.php      |  3 +-
 .../message/QuickReplyManager.class.php       |  7 +--
 .../AbstractModerationQueueHandler.class.php  |  3 +-
 ...actCategoryMultiSelectOptionType.class.php |  3 +-
 .../system/option/FileOptionType.class.php    |  2 +-
 .../lib/system/option/OptionHandler.class.php |  7 +--
 .../option/user/UserOptionHandler.class.php   |  3 +-
 .../group/UserGroupOptionHandler.class.php    |  7 +--
 .../system/package/PackageArchive.class.php   |  2 +-
 .../PackageInstallationDispatcher.class.php   |  4 +-
 .../PackageInstallationScheduler.class.php    |  6 +--
 .../package/PackageUpdateDispatcher.class.php |  2 +-
 ...LOptionPackageInstallationPlugin.class.php |  3 +-
 ...ACPMenuPackageInstallationPlugin.class.php |  3 +-
 ...roviderPackageInstallationPlugin.class.php |  3 +-
 ...dActionPackageInstallationPlugin.class.php |  3 +-
 ...eObjectPackageInstallationPlugin.class.php |  3 +-
 ...CronjobPackageInstallationPlugin.class.php |  2 +-
 ...istenerPackageInstallationPlugin.class.php |  2 +-
 ...initionPackageInstallationPlugin.class.php |  3 +-
 ...ectTypePackageInstallationPlugin.class.php |  3 +-
 .../PIPPackageInstallationPlugin.class.php    |  3 +-
 ...SitemapPackageInstallationPlugin.class.php |  3 +-
 .../SmileyPackageInstallationPlugin.class.php |  3 +-
 .../StylePackageInstallationPlugin.class.php  |  2 +-
 ...istenerPackageInstallationPlugin.class.php |  3 +-
 ...serMenuPackageInstallationPlugin.class.php |  3 +-
 ...onEventPackageInstallationPlugin.class.php |  3 +-
 ...ileMenuPackageInstallationPlugin.class.php |  3 +-
 .../PackageValidationArchive.class.php        |  2 +-
 .../lib/system/poll/PollManager.class.php     |  8 +--
 .../lib/system/search/SearchEngine.class.php  |  7 +--
 .../search/SearchIndexManager.class.php       |  3 +-
 .../search/SearchKeywordManager.class.php     |  3 +-
 .../search/acp/ACPSearchHandler.class.php     |  4 +-
 ...tegorizedACPSearchResultProvider.class.php |  3 +-
 .../MenuItemACPSearchResultProvider.class.php |  3 +-
 .../OptionACPSearchResultProvider.class.php   |  6 ++-
 .../PackageACPSearchResultProvider.class.php  |  3 +-
 .../acp/UserACPSearchResultProvider.class.php |  3 +-
 ...oupOptionACPSearchResultProvider.class.php |  6 ++-
 .../system/session/SessionHandler.class.php   |  3 +-
 .../lib/system/tagging/TagEngine.class.php    |  2 +-
 .../DefaultUserAuthentication.class.php       |  6 +--
 .../IUserAuthentication.class.php             |  4 +-
 .../UserAuthenticationFactory.class.php       |  6 +--
 .../UserNotificationHandler.class.php         |  2 +-
 .../LikeUserNotificationObjectType.class.php  |  9 ++--
 ...FollowUserNotificationObjectType.class.php |  9 ++--
 ...sponseUserNotificationObjectType.class.php |  9 ++--
 ...ommentUserNotificationObjectType.class.php |  9 ++--
 .../AbstractRebuildDataWorker.class.php       |  5 +-
 .../AttachmentRebuildDataWorker.class.php     |  3 +-
 .../worker/LikeRebuildDataWorker.class.php    |  3 +-
 .../LikeUserRebuildDataWorker.class.php       |  3 +-
 .../worker/SendNewPasswordWorker.class.php    |  2 +-
 .../worker/UserRebuildDataWorker.class.php    |  3 +-
 .../files/lib/util/HeaderUtil.class.php       |  4 +-
 211 files changed, 446 insertions(+), 294 deletions(-)

diff --git a/wcfsetup/install/files/lib/acp/action/InstallPackageAction.class.php b/wcfsetup/install/files/lib/acp/action/InstallPackageAction.class.php
index 660891a3d5..5455b9de4a 100755
--- a/wcfsetup/install/files/lib/acp/action/InstallPackageAction.class.php
+++ b/wcfsetup/install/files/lib/acp/action/InstallPackageAction.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\acp\action;
 use wcf\action\AbstractDialogAction;
+use wcf\data\application\Application;
 use wcf\data\package\installation\queue\PackageInstallationQueue;
 use wcf\system\cache\CacheHandler;
 use wcf\system\exception\IllegalLinkException;
@@ -116,7 +117,7 @@ class InstallPackageAction extends AbstractDialogAction {
 					WHERE	packageID = ?";
 				$statement = WCF::getDB()->prepareStatement($sql);
 				$statement->execute([$packageID]);
-				$application = $statement->fetchObject('wcf\data\application\Application');
+				$application = $statement->fetchObject(Application::class);
 				
 				// build redirect location
 				$location = $application->getPageURL() . 'acp/index.php?package-list/';
diff --git a/wcfsetup/install/files/lib/acp/action/UninstallPackageAction.class.php b/wcfsetup/install/files/lib/acp/action/UninstallPackageAction.class.php
index 70591388e8..f854e0fb27 100644
--- a/wcfsetup/install/files/lib/acp/action/UninstallPackageAction.class.php
+++ b/wcfsetup/install/files/lib/acp/action/UninstallPackageAction.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\acp\action;
 use wcf\action\AbstractDialogAction;
+use wcf\data\application\Application;
 use wcf\data\package\installation\queue\PackageInstallationQueue;
 use wcf\data\package\installation\queue\PackageInstallationQueueEditor;
 use wcf\data\package\Package;
@@ -132,7 +133,7 @@ class UninstallPackageAction extends InstallPackageAction {
 				WHERE	packageID = ?";
 			$statement = WCF::getDB()->prepareStatement($sql);
 			$statement->execute([$packageID]);
-			$application = $statement->fetchObject('wcf\data\application\Application');
+			$application = $statement->fetchObject(Application::class);
 			
 			// build redirect location
 			$location = $application->getPageURL() . 'acp/index.php?package-list/';
diff --git a/wcfsetup/install/files/lib/acp/action/WorkerProxyAction.class.php b/wcfsetup/install/files/lib/acp/action/WorkerProxyAction.class.php
index 3c823cb2c3..8c4f6cabc6 100644
--- a/wcfsetup/install/files/lib/acp/action/WorkerProxyAction.class.php
+++ b/wcfsetup/install/files/lib/acp/action/WorkerProxyAction.class.php
@@ -3,6 +3,7 @@ namespace wcf\acp\action;
 use wcf\action\AbstractSecureAction;
 use wcf\action\AJAXInvokeAction;
 use wcf\system\exception\SystemException;
+use wcf\system\worker\IWorker;
 use wcf\system\WCF;
 use wcf\util\JSON;
 
@@ -63,8 +64,8 @@ class WorkerProxyAction extends AJAXInvokeAction {
 			throw new SystemException("class name cannot be empty.");
 		}
 		
-		if (!is_subclass_of($this->className, 'wcf\system\worker\IWorker')) {
-			throw new SystemException("'".$this->className."' does not implement 'wcf\system\worker\IWorker'");
+		if (!is_subclass_of($this->className, IWorker::class)) {
+			throw new SystemException("'".$this->className."' does not implement '".IWorker::class."'");
 		}
 	}
 	
diff --git a/wcfsetup/install/files/lib/acp/form/AbstractOptionListForm.class.php b/wcfsetup/install/files/lib/acp/form/AbstractOptionListForm.class.php
index c4bf1ef69d..c0e78debcf 100755
--- a/wcfsetup/install/files/lib/acp/form/AbstractOptionListForm.class.php
+++ b/wcfsetup/install/files/lib/acp/form/AbstractOptionListForm.class.php
@@ -2,6 +2,7 @@
 namespace wcf\acp\form;
 use wcf\form\AbstractForm;
 use wcf\system\exception\UserInputException;
+use wcf\system\option\OptionHandler;
 
 /**
  * This class provides default implementations for a list of options.
@@ -46,7 +47,7 @@ abstract class AbstractOptionListForm extends AbstractForm {
 	 * option handler class name
 	 * @var	string
 	 */
-	public $optionHandlerClassName = 'wcf\system\option\OptionHandler';
+	public $optionHandlerClassName = OptionHandler::class;
 	
 	/**
 	 * true if option supports i18n
diff --git a/wcfsetup/install/files/lib/acp/form/UserOptionListForm.class.php b/wcfsetup/install/files/lib/acp/form/UserOptionListForm.class.php
index 9eb0f5b426..5419053c73 100644
--- a/wcfsetup/install/files/lib/acp/form/UserOptionListForm.class.php
+++ b/wcfsetup/install/files/lib/acp/form/UserOptionListForm.class.php
@@ -2,6 +2,7 @@
 namespace wcf\acp\form;
 use wcf\data\user\group\UserGroup;
 use wcf\system\language\LanguageFactory;
+use wcf\system\option\user\UserOptionHandler;
 
 /**
  * This class provides default implementations for a list of dynamic user options.
@@ -17,7 +18,7 @@ abstract class UserOptionListForm extends AbstractOptionListForm {
 	/**
 	 * @inheritDoc
 	 */
-	public $optionHandlerClassName = 'wcf\system\option\user\UserOptionHandler';
+	public $optionHandlerClassName = UserOptionHandler::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/ACPSessionLogListPage.class.php b/wcfsetup/install/files/lib/acp/page/ACPSessionLogListPage.class.php
index a19ea7c1fb..f2109f9f3d 100755
--- a/wcfsetup/install/files/lib/acp/page/ACPSessionLogListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/ACPSessionLogListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\acp\session\log\ACPSessionLogList;
 use wcf\page\SortablePage;
 
 /**
@@ -46,7 +47,7 @@ class ACPSessionLogListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\acp\session\log\ACPSessionLogList';
+	public $objectListClassName = ACPSessionLogList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/ACPSessionLogPage.class.php b/wcfsetup/install/files/lib/acp/page/ACPSessionLogPage.class.php
index ae9e46e7d0..62781dc17c 100755
--- a/wcfsetup/install/files/lib/acp/page/ACPSessionLogPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/ACPSessionLogPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\acp\session\access\log\ACPSessionAccessLogList;
 use wcf\data\acp\session\log\ACPSessionLog;
 use wcf\page\SortablePage;
 use wcf\system\exception\IllegalLinkException;
@@ -56,7 +57,7 @@ class ACPSessionLogPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\acp\session\access\log\ACPSessionAccessLogList';
+	public $objectListClassName = ACPSessionAccessLogList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/AdListPage.class.php b/wcfsetup/install/files/lib/acp/page/AdListPage.class.php
index d8275a1b62..5f147e5eca 100644
--- a/wcfsetup/install/files/lib/acp/page/AdListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/AdListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\ad\AdList;
 use wcf\page\MultipleLinkPage;
 
 /**
@@ -31,7 +32,7 @@ class AdListPage extends MultipleLinkPage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\ad\AdList';
+	public $objectListClassName = AdList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/AttachmentListPage.class.php b/wcfsetup/install/files/lib/acp/page/AttachmentListPage.class.php
index 28b0ba29ca..f40e63d16c 100644
--- a/wcfsetup/install/files/lib/acp/page/AttachmentListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/AttachmentListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\attachment\AdministrativeAttachmentList;
 use wcf\data\object\type\ObjectTypeCache;
 use wcf\data\user\User;
 use wcf\page\SortablePage;
@@ -45,7 +46,7 @@ class AttachmentListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\attachment\AdministrativeAttachmentList';
+	public $objectListClassName = AdministrativeAttachmentList::class;
 	
 	/**
 	 * username
diff --git a/wcfsetup/install/files/lib/acp/page/BBCodeListPage.class.php b/wcfsetup/install/files/lib/acp/page/BBCodeListPage.class.php
index bf85d8441c..1c78b28fa0 100644
--- a/wcfsetup/install/files/lib/acp/page/BBCodeListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/BBCodeListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\bbcode\BBCodeList;
 use wcf\page\SortablePage;
 
 /**
@@ -31,7 +32,7 @@ class BBCodeListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\bbcode\BBCodeList';
+	public $objectListClassName = BBCodeList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/BBCodeMediaProviderListPage.class.php b/wcfsetup/install/files/lib/acp/page/BBCodeMediaProviderListPage.class.php
index c1192523b9..3b94686919 100644
--- a/wcfsetup/install/files/lib/acp/page/BBCodeMediaProviderListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/BBCodeMediaProviderListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\bbcode\media\provider\BBCodeMediaProviderList;
 use wcf\page\SortablePage;
 
 /**
@@ -31,7 +32,7 @@ class BBCodeMediaProviderListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\bbcode\media\provider\BBCodeMediaProviderList';
+	public $objectListClassName = BBCodeMediaProviderList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/BoxListPage.class.php b/wcfsetup/install/files/lib/acp/page/BoxListPage.class.php
index edb211022e..c2e7dc6bee 100644
--- a/wcfsetup/install/files/lib/acp/page/BoxListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/BoxListPage.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\acp\page;
 use wcf\data\box\Box;
+use wcf\data\box\BoxList;
 use wcf\page\SortablePage;
 use wcf\system\WCF;
 use wcf\util\StringUtil;
@@ -25,7 +26,7 @@ class BoxListPage extends SortablePage {
 	/**
 	 * @inheritdoc
 	 */
-	public $objectListClassName = 'wcf\data\box\BoxList';
+	public $objectListClassName = BoxList::class;
 	
 	/**
 	 * @inheritdoc
diff --git a/wcfsetup/install/files/lib/acp/page/CaptchaQuestionListPage.class.php b/wcfsetup/install/files/lib/acp/page/CaptchaQuestionListPage.class.php
index 95a42aee48..f21efc9fb0 100644
--- a/wcfsetup/install/files/lib/acp/page/CaptchaQuestionListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/CaptchaQuestionListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\captcha\question\CaptchaQuestionList;
 use wcf\page\MultipleLinkPage;
 
 /**
@@ -26,7 +27,7 @@ class CaptchaQuestionListPage extends MultipleLinkPage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\captcha\question\CaptchaQuestionList';
+	public $objectListClassName = CaptchaQuestionList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/CronjobListPage.class.php b/wcfsetup/install/files/lib/acp/page/CronjobListPage.class.php
index cce7f5ee46..5767e43fb9 100755
--- a/wcfsetup/install/files/lib/acp/page/CronjobListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/CronjobListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\cronjob\CronjobList;
 use wcf\page\SortablePage;
 
 /**
@@ -36,7 +37,7 @@ class CronjobListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\cronjob\CronjobList';
+	public $objectListClassName = CronjobList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/CronjobLogListPage.class.php b/wcfsetup/install/files/lib/acp/page/CronjobLogListPage.class.php
index ccaf43730b..52ee9ec69f 100755
--- a/wcfsetup/install/files/lib/acp/page/CronjobLogListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/CronjobLogListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\cronjob\log\CronjobLogList;
 use wcf\page\SortablePage;
 
 /**
@@ -46,7 +47,7 @@ class CronjobLogListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\cronjob\log\CronjobLogList';
+	public $objectListClassName = CronjobLogList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/LabelGroupListPage.class.php b/wcfsetup/install/files/lib/acp/page/LabelGroupListPage.class.php
index 6daed565a6..477d73db75 100644
--- a/wcfsetup/install/files/lib/acp/page/LabelGroupListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/LabelGroupListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\label\group\LabelGroupList;
 use wcf\page\SortablePage;
 
 /**
@@ -36,5 +37,5 @@ class LabelGroupListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\label\group\LabelGroupList';
+	public $objectListClassName = LabelGroupList::class;
 }
diff --git a/wcfsetup/install/files/lib/acp/page/LanguageListPage.class.php b/wcfsetup/install/files/lib/acp/page/LanguageListPage.class.php
index 18459e80df..d387a36ad6 100644
--- a/wcfsetup/install/files/lib/acp/page/LanguageListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/LanguageListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\language\LanguageList;
 use wcf\page\SortablePage;
 use wcf\system\WCF;
 
@@ -32,7 +33,7 @@ class LanguageListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\language\LanguageList';
+	public $objectListClassName = LanguageList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/MenuListPage.class.php b/wcfsetup/install/files/lib/acp/page/MenuListPage.class.php
index 37a66eeba9..60d6d72f96 100644
--- a/wcfsetup/install/files/lib/acp/page/MenuListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/MenuListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\menu\MenuList;
 use wcf\page\SortablePage;
 
 /**
@@ -22,7 +23,7 @@ class MenuListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\menu\MenuList';
+	public $objectListClassName = MenuList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/NoticeListPage.class.php b/wcfsetup/install/files/lib/acp/page/NoticeListPage.class.php
index 3b55c68ae0..fb6ae987d0 100644
--- a/wcfsetup/install/files/lib/acp/page/NoticeListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/NoticeListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\notice\NoticeList;
 use wcf\page\SortablePage;
 
 /**
@@ -31,7 +32,7 @@ class NoticeListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\notice\NoticeList';
+	public $objectListClassName = NoticeList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/PackageListPage.class.php b/wcfsetup/install/files/lib/acp/page/PackageListPage.class.php
index 6781bf9a77..611aac24c0 100644
--- a/wcfsetup/install/files/lib/acp/page/PackageListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/PackageListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\package\PackageList;
 use wcf\page\SortablePage;
 use wcf\system\WCF;
 
@@ -53,7 +54,7 @@ class PackageListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\package\PackageList';
+	public $objectListClassName = PackageList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/PackageUpdateServerListPage.class.php b/wcfsetup/install/files/lib/acp/page/PackageUpdateServerListPage.class.php
index 569186b7d5..3d72f1738a 100755
--- a/wcfsetup/install/files/lib/acp/page/PackageUpdateServerListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/PackageUpdateServerListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\package\update\server\PackageUpdateServerList;
 use wcf\page\SortablePage;
 
 /**
@@ -36,7 +37,7 @@ class PackageUpdateServerListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\package\update\server\PackageUpdateServerList';
+	public $objectListClassName = PackageUpdateServerList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/PageListPage.class.php b/wcfsetup/install/files/lib/acp/page/PageListPage.class.php
index c0e16b7d2c..87c5e16c70 100644
--- a/wcfsetup/install/files/lib/acp/page/PageListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/PageListPage.class.php
@@ -2,6 +2,7 @@
 namespace wcf\acp\page;
 use wcf\data\application\Application;
 use wcf\data\application\ApplicationList;
+use wcf\data\page\PageList;
 use wcf\page\SortablePage;
 use wcf\system\WCF;
 use wcf\util\StringUtil;
@@ -26,7 +27,7 @@ class PageListPage extends SortablePage {
 	/**
 	 * @inheritdoc
 	 */
-	public $objectListClassName = 'wcf\data\page\PageList';
+	public $objectListClassName = PageList::class;
 	
 	/**
 	 * @inheritdoc
diff --git a/wcfsetup/install/files/lib/acp/page/PaidSubscriptionListPage.class.php b/wcfsetup/install/files/lib/acp/page/PaidSubscriptionListPage.class.php
index ce988b03d4..170c65c21f 100644
--- a/wcfsetup/install/files/lib/acp/page/PaidSubscriptionListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/PaidSubscriptionListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\paid\subscription\PaidSubscriptionList;
 use wcf\page\SortablePage;
 
 /**
@@ -41,5 +42,5 @@ class PaidSubscriptionListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\paid\subscription\PaidSubscriptionList';
+	public $objectListClassName = PaidSubscriptionList::class;
 }
diff --git a/wcfsetup/install/files/lib/acp/page/PaidSubscriptionTransactionLogListPage.class.php b/wcfsetup/install/files/lib/acp/page/PaidSubscriptionTransactionLogListPage.class.php
index 0adec277b2..f86aa0c4ea 100644
--- a/wcfsetup/install/files/lib/acp/page/PaidSubscriptionTransactionLogListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/PaidSubscriptionTransactionLogListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\paid\subscription\transaction\log\PaidSubscriptionTransactionLogList;
 use wcf\page\SortablePage;
 use wcf\system\cache\builder\PaidSubscriptionCacheBuilder;
 use wcf\system\WCF;
@@ -49,7 +50,7 @@ class PaidSubscriptionTransactionLogListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\paid\subscription\transaction\log\PaidSubscriptionTransactionLogList';
+	public $objectListClassName = PaidSubscriptionTransactionLogList::class;
 	
 	/**
 	 * transaction id
diff --git a/wcfsetup/install/files/lib/acp/page/PaidSubscriptionUserListPage.class.php b/wcfsetup/install/files/lib/acp/page/PaidSubscriptionUserListPage.class.php
index 8dacbd9a2f..b040515f5e 100644
--- a/wcfsetup/install/files/lib/acp/page/PaidSubscriptionUserListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/PaidSubscriptionUserListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\paid\subscription\user\PaidSubscriptionUserList;
 use wcf\page\SortablePage;
 
 /**
@@ -41,7 +42,7 @@ class PaidSubscriptionUserListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\paid\subscription\user\PaidSubscriptionUserList';
+	public $objectListClassName = PaidSubscriptionUserList::class;
 	
 	/**
 	 * Initializes DatabaseObjectList instance.
diff --git a/wcfsetup/install/files/lib/acp/page/SmileyListPage.class.php b/wcfsetup/install/files/lib/acp/page/SmileyListPage.class.php
index 496ef03d12..419304ecb2 100644
--- a/wcfsetup/install/files/lib/acp/page/SmileyListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/SmileyListPage.class.php
@@ -3,6 +3,7 @@ namespace wcf\acp\page;
 use wcf\data\category\Category;
 use wcf\data\smiley\category\SmileyCategory;
 use wcf\data\smiley\SmileyCache;
+use wcf\data\smiley\SmileyList;
 use wcf\page\MultipleLinkPage;
 use wcf\system\exception\IllegalLinkException;
 use wcf\system\WCF;
@@ -36,7 +37,7 @@ class SmileyListPage extends MultipleLinkPage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\smiley\SmileyList';
+	public $objectListClassName = SmileyList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/StyleListPage.class.php b/wcfsetup/install/files/lib/acp/page/StyleListPage.class.php
index 389db1778c..25b5a663dd 100644
--- a/wcfsetup/install/files/lib/acp/page/StyleListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/StyleListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\style\StyleList;
 use wcf\page\MultipleLinkPage;
 
 /**
@@ -26,7 +27,7 @@ class StyleListPage extends MultipleLinkPage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\style\StyleList';
+	public $objectListClassName = StyleList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/TagListPage.class.php b/wcfsetup/install/files/lib/acp/page/TagListPage.class.php
index 3054542196..2d79212fbc 100644
--- a/wcfsetup/install/files/lib/acp/page/TagListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/TagListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\tag\TagList;
 use wcf\page\SortablePage;
 use wcf\system\clipboard\ClipboardHandler;
 use wcf\system\WCF;
@@ -44,7 +45,7 @@ class TagListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\tag\TagList';
+	public $objectListClassName = TagList::class;
 	
 	/**
 	 * search-query
diff --git a/wcfsetup/install/files/lib/acp/page/TemplateGroupListPage.class.php b/wcfsetup/install/files/lib/acp/page/TemplateGroupListPage.class.php
index a10378ce83..12fbef8a06 100644
--- a/wcfsetup/install/files/lib/acp/page/TemplateGroupListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/TemplateGroupListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\template\group\TemplateGroupList;
 use wcf\page\SortablePage;
 
 /**
@@ -31,7 +32,7 @@ class TemplateGroupListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\template\group\TemplateGroupList';
+	public $objectListClassName = TemplateGroupList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/TemplateListPage.class.php b/wcfsetup/install/files/lib/acp/page/TemplateListPage.class.php
index f6a6e7cf33..8206eb396c 100644
--- a/wcfsetup/install/files/lib/acp/page/TemplateListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/TemplateListPage.class.php
@@ -2,6 +2,7 @@
 namespace wcf\acp\page;
 use wcf\data\package\PackageCache;
 use wcf\data\template\group\TemplateGroup;
+use wcf\data\template\TemplateList;
 use wcf\page\SortablePage;
 use wcf\system\application\ApplicationHandler;
 use wcf\system\WCF;
@@ -31,7 +32,7 @@ class TemplateListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\template\TemplateList';
+	public $objectListClassName = TemplateList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/UserAuthenticationFailureListPage.class.php b/wcfsetup/install/files/lib/acp/page/UserAuthenticationFailureListPage.class.php
index e282e87254..b30cc34bde 100644
--- a/wcfsetup/install/files/lib/acp/page/UserAuthenticationFailureListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/UserAuthenticationFailureListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\user\authentication\failure\UserAuthenticationFailureList;
 use wcf\page\SortablePage;
 
 /**
@@ -46,5 +47,5 @@ class UserAuthenticationFailureListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\user\authentication\failure\UserAuthenticationFailureList';
+	public $objectListClassName = UserAuthenticationFailureList::class;
 }
diff --git a/wcfsetup/install/files/lib/acp/page/UserGroupAssignmentListPage.class.php b/wcfsetup/install/files/lib/acp/page/UserGroupAssignmentListPage.class.php
index 28407b88e2..3bf1356bf1 100644
--- a/wcfsetup/install/files/lib/acp/page/UserGroupAssignmentListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/UserGroupAssignmentListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\user\group\assignment\UserGroupAssignmentList;
 use wcf\page\MultipleLinkPage;
 
 /**
@@ -26,5 +27,5 @@ class UserGroupAssignmentListPage extends MultipleLinkPage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\user\group\assignment\UserGroupAssignmentList';
+	public $objectListClassName = UserGroupAssignmentList::class;
 }
diff --git a/wcfsetup/install/files/lib/acp/page/UserGroupListPage.class.php b/wcfsetup/install/files/lib/acp/page/UserGroupListPage.class.php
index 6bf4aee49a..9ee7d382d6 100755
--- a/wcfsetup/install/files/lib/acp/page/UserGroupListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/UserGroupListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\user\group\UserGroupList;
 use wcf\page\SortablePage;
 use wcf\system\WCF;
 
@@ -37,7 +38,7 @@ class UserGroupListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\user\group\UserGroupList';
+	public $objectListClassName = UserGroupList::class;
 	
 	/**
 	 * indicates if a group has just been deleted
diff --git a/wcfsetup/install/files/lib/acp/page/UserOptionCategoryListPage.class.php b/wcfsetup/install/files/lib/acp/page/UserOptionCategoryListPage.class.php
index 0a6cc5cb26..0f43df81f9 100644
--- a/wcfsetup/install/files/lib/acp/page/UserOptionCategoryListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/UserOptionCategoryListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\user\option\category\UserOptionCategoryList;
 use wcf\page\SortablePage;
 
 /**
@@ -31,7 +32,7 @@ class UserOptionCategoryListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\user\option\category\UserOptionCategoryList';
+	public $objectListClassName = UserOptionCategoryList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/UserOptionListPage.class.php b/wcfsetup/install/files/lib/acp/page/UserOptionListPage.class.php
index c4b2abe31c..43530bffeb 100644
--- a/wcfsetup/install/files/lib/acp/page/UserOptionListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/UserOptionListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\user\option\UserOptionList;
 use wcf\page\SortablePage;
 
 /**
@@ -31,7 +32,7 @@ class UserOptionListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\user\option\UserOptionList';
+	public $objectListClassName = UserOptionList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/acp/page/UserRankListPage.class.php b/wcfsetup/install/files/lib/acp/page/UserRankListPage.class.php
index 4722b43433..b196b676b5 100644
--- a/wcfsetup/install/files/lib/acp/page/UserRankListPage.class.php
+++ b/wcfsetup/install/files/lib/acp/page/UserRankListPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\acp\page;
+use wcf\data\user\rank\UserRankList;
 use wcf\page\SortablePage;
 
 /**
@@ -31,7 +32,7 @@ class UserRankListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\user\rank\UserRankList';
+	public $objectListClassName = UserRankList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/action/AJAXProxyAction.class.php b/wcfsetup/install/files/lib/action/AJAXProxyAction.class.php
index 3f27fd7353..d8c8e5bf98 100644
--- a/wcfsetup/install/files/lib/action/AJAXProxyAction.class.php
+++ b/wcfsetup/install/files/lib/action/AJAXProxyAction.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\action;
+use wcf\data\IDatabaseObjectAction;
 use wcf\system\exception\SystemException;
 use wcf\system\WCF;
 use wcf\util\ArrayUtil;
@@ -55,8 +56,8 @@ class AJAXProxyAction extends AJAXInvokeAction {
 	 * @inheritDoc
 	 */
 	protected function invoke() {
-		if (!is_subclass_of($this->className, 'wcf\data\IDatabaseObjectAction')) {
-			throw new SystemException("'".$this->className."' does not implement 'wcf\data\IDatabaseObjectAction'");
+		if (!is_subclass_of($this->className, IDatabaseObjectAction::class)) {
+			throw new SystemException("'".$this->className."' does not implement '".IDatabaseObjectAction::class."'");
 		}
 		
 		if (!empty($this->interfaceName)) {
diff --git a/wcfsetup/install/files/lib/data/AbstractDatabaseObjectAction.class.php b/wcfsetup/install/files/lib/data/AbstractDatabaseObjectAction.class.php
index 4c5919b4d3..951d872ed9 100644
--- a/wcfsetup/install/files/lib/data/AbstractDatabaseObjectAction.class.php
+++ b/wcfsetup/install/files/lib/data/AbstractDatabaseObjectAction.class.php
@@ -214,7 +214,7 @@ abstract class AbstractDatabaseObjectAction implements IDatabaseObjectAction, ID
 	 * Resets cache of database object.
 	 */
 	protected function resetCache() {
-		if (is_subclass_of($this->className, 'wcf\data\IEditableCachedObject')) {
+		if (is_subclass_of($this->className, IEditableCachedObject::class)) {
 			call_user_func([$this->className, 'resetCache']);
 		}
 	}
diff --git a/wcfsetup/install/files/lib/data/DatabaseObjectList.class.php b/wcfsetup/install/files/lib/data/DatabaseObjectList.class.php
index 0aaaea63eb..748d7a581b 100644
--- a/wcfsetup/install/files/lib/data/DatabaseObjectList.class.php
+++ b/wcfsetup/install/files/lib/data/DatabaseObjectList.class.php
@@ -121,8 +121,8 @@ abstract class DatabaseObjectList implements \Countable, ITraversableObject {
 		
 		if (!empty($this->decoratorClassName)) {
 			// validate decorator class name
-			if (!is_subclass_of($this->decoratorClassName, 'wcf\data\DatabaseObjectDecorator')) {
-				throw new SystemException("'".$this->decoratorClassName."' should extend 'wcf\data\DatabaseObjectDecorator'");
+			if (!is_subclass_of($this->decoratorClassName, DatabaseObjectDecorator::class)) {
+				throw new SystemException("'".$this->decoratorClassName."' should extend '".DatabaseObjectDecorator::class."'");
 			}
 			
 			$objectClassName = $this->objectClassName ?: $this->className;
diff --git a/wcfsetup/install/files/lib/data/ProcessibleDatabaseObject.class.php b/wcfsetup/install/files/lib/data/ProcessibleDatabaseObject.class.php
index a93e557166..9bc0d4f995 100644
--- a/wcfsetup/install/files/lib/data/ProcessibleDatabaseObject.class.php
+++ b/wcfsetup/install/files/lib/data/ProcessibleDatabaseObject.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\data;
 use wcf\system\exception\SystemException;
+use wcf\system\SingletonFactory;
 
 /**
  * Abstract class for all processible data holder classes.
@@ -41,12 +42,12 @@ class ProcessibleDatabaseObject extends DatabaseObject {
 					throw new SystemException("'".$this->className."' does not implement '".static::$processorInterface."'");
 				}
 				
-				if (is_subclass_of($this->className, 'wcf\system\SingletonFactory')) {
+				if (is_subclass_of($this->className, SingletonFactory::class)) {
 					$this->processor = call_user_func([$this->className, 'getInstance']);
 				}
 				else {
-					if (!is_subclass_of($this->className, 'wcf\data\IDatabaseObjectProcessor')) {
-						throw new SystemException("'".$this->className."' does not implement 'wcf\data\IDatabaseObjectProcessor'");
+					if (!is_subclass_of($this->className, IDatabaseObjectProcessor::class)) {
+						throw new SystemException("'".$this->className."' does not implement '".IDatabaseObjectProcessor::class."'");
 					}
 					
 					$this->processor = new $this->className($this);
diff --git a/wcfsetup/install/files/lib/data/acl/option/ACLOptionAction.class.php b/wcfsetup/install/files/lib/data/acl/option/ACLOptionAction.class.php
index a892031ff8..0fce333d7e 100644
--- a/wcfsetup/install/files/lib/data/acl/option/ACLOptionAction.class.php
+++ b/wcfsetup/install/files/lib/data/acl/option/ACLOptionAction.class.php
@@ -17,7 +17,7 @@ class ACLOptionAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\acl\option\ACLOptionEditor';
+	protected $className = ACLOptionEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/acl/option/category/ACLOptionCategoryAction.class.php b/wcfsetup/install/files/lib/data/acl/option/category/ACLOptionCategoryAction.class.php
index e8522ddff2..9b2ed408cb 100644
--- a/wcfsetup/install/files/lib/data/acl/option/category/ACLOptionCategoryAction.class.php
+++ b/wcfsetup/install/files/lib/data/acl/option/category/ACLOptionCategoryAction.class.php
@@ -16,5 +16,5 @@ class ACLOptionCategoryAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\acl\option\category\ACLOptionCategoryEditor';
+	protected $className = ACLOptionCategoryEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/acp/menu/item/ACPMenuItemAction.class.php b/wcfsetup/install/files/lib/data/acp/menu/item/ACPMenuItemAction.class.php
index bd2af37bc2..4f8d416203 100644
--- a/wcfsetup/install/files/lib/data/acp/menu/item/ACPMenuItemAction.class.php
+++ b/wcfsetup/install/files/lib/data/acp/menu/item/ACPMenuItemAction.class.php
@@ -16,5 +16,5 @@ class ACPMenuItemAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\acp\menu\item\ACPMenuItemEditor';
+	protected $className = ACPMenuItemEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/acp/session/access/log/ACPSessionAccessLogAction.class.php b/wcfsetup/install/files/lib/data/acp/session/access/log/ACPSessionAccessLogAction.class.php
index 9aa8d5e57d..b581c2b55f 100644
--- a/wcfsetup/install/files/lib/data/acp/session/access/log/ACPSessionAccessLogAction.class.php
+++ b/wcfsetup/install/files/lib/data/acp/session/access/log/ACPSessionAccessLogAction.class.php
@@ -16,5 +16,5 @@ class ACPSessionAccessLogAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\acp\session\access\log\ACPSessionAccessLogEditor';
+	protected $className = ACPSessionAccessLogEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/acp/session/log/ACPSessionLogAction.class.php b/wcfsetup/install/files/lib/data/acp/session/log/ACPSessionLogAction.class.php
index 8cb33e17d8..9a1d1a21fb 100644
--- a/wcfsetup/install/files/lib/data/acp/session/log/ACPSessionLogAction.class.php
+++ b/wcfsetup/install/files/lib/data/acp/session/log/ACPSessionLogAction.class.php
@@ -16,5 +16,5 @@ class ACPSessionLogAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\acp\session\log\ACPSessionLogEditor';
+	protected $className = ACPSessionLogEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/acp/template/ACPTemplateAction.class.php b/wcfsetup/install/files/lib/data/acp/template/ACPTemplateAction.class.php
index d07f81da3d..f1a20bc434 100644
--- a/wcfsetup/install/files/lib/data/acp/template/ACPTemplateAction.class.php
+++ b/wcfsetup/install/files/lib/data/acp/template/ACPTemplateAction.class.php
@@ -16,7 +16,7 @@ class ACPTemplateAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\acp\template\ACPTemplateEditor';
+	protected $className = ACPTemplateEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/bbcode/BBCodeAction.class.php b/wcfsetup/install/files/lib/data/bbcode/BBCodeAction.class.php
index 7185725d02..21d68fa704 100644
--- a/wcfsetup/install/files/lib/data/bbcode/BBCodeAction.class.php
+++ b/wcfsetup/install/files/lib/data/bbcode/BBCodeAction.class.php
@@ -22,7 +22,7 @@ class BBCodeAction extends AbstractDatabaseObjectAction implements IToggleAction
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\bbcode\BBCodeEditor';
+	protected $className = BBCodeEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/bbcode/attribute/BBCodeAttributeAction.class.php b/wcfsetup/install/files/lib/data/bbcode/attribute/BBCodeAttributeAction.class.php
index 5c20b2a800..203d423f85 100644
--- a/wcfsetup/install/files/lib/data/bbcode/attribute/BBCodeAttributeAction.class.php
+++ b/wcfsetup/install/files/lib/data/bbcode/attribute/BBCodeAttributeAction.class.php
@@ -16,5 +16,5 @@ class BBCodeAttributeAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\bbcode\attribute\BBCodeAttributeEditor';
+	protected $className = BBCodeAttributeEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/bbcode/media/provider/BBCodeMediaProviderAction.class.php b/wcfsetup/install/files/lib/data/bbcode/media/provider/BBCodeMediaProviderAction.class.php
index 68af603c99..c18b5a3720 100644
--- a/wcfsetup/install/files/lib/data/bbcode/media/provider/BBCodeMediaProviderAction.class.php
+++ b/wcfsetup/install/files/lib/data/bbcode/media/provider/BBCodeMediaProviderAction.class.php
@@ -16,7 +16,7 @@ class BBCodeMediaProviderAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\bbcode\media\provider\BBCodeMediaProviderEditor';
+	protected $className = BBCodeMediaProviderEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/category/CategoryNodeTree.class.php b/wcfsetup/install/files/lib/data/category/CategoryNodeTree.class.php
index e40d92cf7b..bdb93cd9e2 100644
--- a/wcfsetup/install/files/lib/data/category/CategoryNodeTree.class.php
+++ b/wcfsetup/install/files/lib/data/category/CategoryNodeTree.class.php
@@ -168,7 +168,7 @@ class CategoryNodeTree implements \IteratorAggregate {
 		
 		// decorate category if necessary
 		$decoratorClassName = call_user_func([$this->nodeClassName, 'getBaseClass']);
-		if ($decoratorClassName != 'wcf\data\category\Category') {
+		if ($decoratorClassName != Category::class) {
 			$category = new $decoratorClassName($category);
 		}
 		
diff --git a/wcfsetup/install/files/lib/data/clipboard/action/ClipboardActionAction.class.php b/wcfsetup/install/files/lib/data/clipboard/action/ClipboardActionAction.class.php
index 02f230f8ec..182369dd65 100644
--- a/wcfsetup/install/files/lib/data/clipboard/action/ClipboardActionAction.class.php
+++ b/wcfsetup/install/files/lib/data/clipboard/action/ClipboardActionAction.class.php
@@ -16,5 +16,5 @@ class ClipboardActionAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\clipboard\action\ClipboardActionEditor';
+	protected $className = ClipboardActionEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/comment/response/CommentResponseAction.class.php b/wcfsetup/install/files/lib/data/comment/response/CommentResponseAction.class.php
index 408db25264..e90998826d 100644
--- a/wcfsetup/install/files/lib/data/comment/response/CommentResponseAction.class.php
+++ b/wcfsetup/install/files/lib/data/comment/response/CommentResponseAction.class.php
@@ -31,7 +31,7 @@ class CommentResponseAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\comment\response\CommentResponseEditor';
+	protected $className = CommentResponseEditor::class;
 	
 	/**
 	 * comment object
diff --git a/wcfsetup/install/files/lib/data/core/object/CoreObjectAction.class.php b/wcfsetup/install/files/lib/data/core/object/CoreObjectAction.class.php
index c9d4fac86a..497bd0061f 100644
--- a/wcfsetup/install/files/lib/data/core/object/CoreObjectAction.class.php
+++ b/wcfsetup/install/files/lib/data/core/object/CoreObjectAction.class.php
@@ -16,5 +16,5 @@ class CoreObjectAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\core\object\CoreObjectEditor';
+	protected $className = CoreObjectEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/cronjob/CronjobAction.class.php b/wcfsetup/install/files/lib/data/cronjob/CronjobAction.class.php
index 21d9d67857..52f471384a 100644
--- a/wcfsetup/install/files/lib/data/cronjob/CronjobAction.class.php
+++ b/wcfsetup/install/files/lib/data/cronjob/CronjobAction.class.php
@@ -23,7 +23,7 @@ class CronjobAction extends AbstractDatabaseObjectAction implements IToggleActio
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\cronjob\CronjobEditor';
+	protected $className = CronjobEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/cronjob/CronjobEditor.class.php b/wcfsetup/install/files/lib/data/cronjob/CronjobEditor.class.php
index 9bf321638d..6b42606846 100644
--- a/wcfsetup/install/files/lib/data/cronjob/CronjobEditor.class.php
+++ b/wcfsetup/install/files/lib/data/cronjob/CronjobEditor.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\data\cronjob;
+use wcf\data\language\category\LanguageCategory;
 use wcf\data\language\LanguageList;
 use wcf\data\DatabaseObjectEditor;
 use wcf\data\IEditableCachedObject;
@@ -84,7 +85,7 @@ class CronjobEditor extends DatabaseObjectEditor implements IEditableCachedObjec
 				WHERE	languageCategory = ?";
 			$statement = WCF::getDB()->prepareStatement($sql);
 			$statement->execute(['wcf.acp.cronjob']);
-			$languageCategory = $statement->fetchObject('wcf\data\language\category\LanguageCategory');
+			$languageCategory = $statement->fetchObject(LanguageCategory::class);
 			
 			$languages = new LanguageList();
 			$languages->readObjects();
diff --git a/wcfsetup/install/files/lib/data/cronjob/log/CronjobLogAction.class.php b/wcfsetup/install/files/lib/data/cronjob/log/CronjobLogAction.class.php
index 8f77de50dc..ee073a7296 100644
--- a/wcfsetup/install/files/lib/data/cronjob/log/CronjobLogAction.class.php
+++ b/wcfsetup/install/files/lib/data/cronjob/log/CronjobLogAction.class.php
@@ -17,7 +17,7 @@ class CronjobLogAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\cronjob\log\CronjobLogEditor';
+	protected $className = CronjobLogEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/edit/history/entry/EditHistoryEntryAction.class.php b/wcfsetup/install/files/lib/data/edit/history/entry/EditHistoryEntryAction.class.php
index 5b6f268575..a50448911a 100644
--- a/wcfsetup/install/files/lib/data/edit/history/entry/EditHistoryEntryAction.class.php
+++ b/wcfsetup/install/files/lib/data/edit/history/entry/EditHistoryEntryAction.class.php
@@ -18,7 +18,7 @@ class EditHistoryEntryAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\edit\history\entry\EditHistoryEntryEditor';
+	protected $className = EditHistoryEntryEditor::class;
 	
 	/**
 	 * Checks permissions to revert.
diff --git a/wcfsetup/install/files/lib/data/event/listener/EventListenerAction.class.php b/wcfsetup/install/files/lib/data/event/listener/EventListenerAction.class.php
index 86f5f94ff6..83dda923cd 100644
--- a/wcfsetup/install/files/lib/data/event/listener/EventListenerAction.class.php
+++ b/wcfsetup/install/files/lib/data/event/listener/EventListenerAction.class.php
@@ -16,5 +16,5 @@ class EventListenerAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\event\listener\EventListenerEditor';
+	protected $className = EventListenerEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/label/group/LabelGroupAction.class.php b/wcfsetup/install/files/lib/data/label/group/LabelGroupAction.class.php
index b5d1e23632..8847db4970 100644
--- a/wcfsetup/install/files/lib/data/label/group/LabelGroupAction.class.php
+++ b/wcfsetup/install/files/lib/data/label/group/LabelGroupAction.class.php
@@ -17,7 +17,7 @@ class LabelGroupAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\label\group\LabelGroupEditor';
+	protected $className = LabelGroupEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/language/LanguageAction.class.php b/wcfsetup/install/files/lib/data/language/LanguageAction.class.php
index 8c9a126e7b..ff42f99d59 100644
--- a/wcfsetup/install/files/lib/data/language/LanguageAction.class.php
+++ b/wcfsetup/install/files/lib/data/language/LanguageAction.class.php
@@ -17,7 +17,7 @@ class LanguageAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\language\LanguageEditor';
+	protected $className = LanguageEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/language/category/LanguageCategoryAction.class.php b/wcfsetup/install/files/lib/data/language/category/LanguageCategoryAction.class.php
index 0227e39541..812475fd17 100644
--- a/wcfsetup/install/files/lib/data/language/category/LanguageCategoryAction.class.php
+++ b/wcfsetup/install/files/lib/data/language/category/LanguageCategoryAction.class.php
@@ -16,7 +16,7 @@ class LanguageCategoryAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\language\category\LanguageCategoryEditor';
+	protected $className = LanguageCategoryEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/language/item/LanguageItemAction.class.php b/wcfsetup/install/files/lib/data/language/item/LanguageItemAction.class.php
index 8b276b6a2d..50fedbd656 100644
--- a/wcfsetup/install/files/lib/data/language/item/LanguageItemAction.class.php
+++ b/wcfsetup/install/files/lib/data/language/item/LanguageItemAction.class.php
@@ -20,7 +20,7 @@ class LanguageItemAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\language\item\LanguageItemEditor';
+	protected $className = LanguageItemEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/like/LikeAction.class.php b/wcfsetup/install/files/lib/data/like/LikeAction.class.php
index 13b2d27e4f..f39d835bd9 100644
--- a/wcfsetup/install/files/lib/data/like/LikeAction.class.php
+++ b/wcfsetup/install/files/lib/data/like/LikeAction.class.php
@@ -33,7 +33,7 @@ class LikeAction extends AbstractDatabaseObjectAction implements IGroupedUserLis
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\like\LikeEditor';
+	protected $className = LikeEditor::class;
 	
 	/**
 	 * likeable object
diff --git a/wcfsetup/install/files/lib/data/moderation/queue/ModerationQueueAction.class.php b/wcfsetup/install/files/lib/data/moderation/queue/ModerationQueueAction.class.php
index f3916c93f2..51811f9e51 100644
--- a/wcfsetup/install/files/lib/data/moderation/queue/ModerationQueueAction.class.php
+++ b/wcfsetup/install/files/lib/data/moderation/queue/ModerationQueueAction.class.php
@@ -26,7 +26,7 @@ class ModerationQueueAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\moderation\queue\ModerationQueueEditor';
+	protected $className = ModerationQueueEditor::class;
 	
 	/**
 	 * moderation queue editor object
diff --git a/wcfsetup/install/files/lib/data/object/type/ObjectTypeAction.class.php b/wcfsetup/install/files/lib/data/object/type/ObjectTypeAction.class.php
index c9304bf961..6073861bcd 100644
--- a/wcfsetup/install/files/lib/data/object/type/ObjectTypeAction.class.php
+++ b/wcfsetup/install/files/lib/data/object/type/ObjectTypeAction.class.php
@@ -16,5 +16,5 @@ class ObjectTypeAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\object\type\ObjectTypeEditor';
+	protected $className = ObjectTypeEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/object/type/definition/ObjectTypeDefinitionAction.class.php b/wcfsetup/install/files/lib/data/object/type/definition/ObjectTypeDefinitionAction.class.php
index cdf3482fc3..433d578c87 100644
--- a/wcfsetup/install/files/lib/data/object/type/definition/ObjectTypeDefinitionAction.class.php
+++ b/wcfsetup/install/files/lib/data/object/type/definition/ObjectTypeDefinitionAction.class.php
@@ -16,5 +16,5 @@ class ObjectTypeDefinitionAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\object\type\definition\ObjectTypeDefinitionEditor';
+	protected $className = ObjectTypeDefinitionEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/option/OptionAction.class.php b/wcfsetup/install/files/lib/data/option/OptionAction.class.php
index e8de4d02a4..810fb04357 100644
--- a/wcfsetup/install/files/lib/data/option/OptionAction.class.php
+++ b/wcfsetup/install/files/lib/data/option/OptionAction.class.php
@@ -16,7 +16,7 @@ class OptionAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\option\OptionEditor';
+	protected $className = OptionEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/option/category/OptionCategoryAction.class.php b/wcfsetup/install/files/lib/data/option/category/OptionCategoryAction.class.php
index 24dff29884..d586c65fdf 100644
--- a/wcfsetup/install/files/lib/data/option/category/OptionCategoryAction.class.php
+++ b/wcfsetup/install/files/lib/data/option/category/OptionCategoryAction.class.php
@@ -16,7 +16,7 @@ class OptionCategoryAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\option\category\OptionCategoryEditor';
+	protected $className = OptionCategoryEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/package/PackageAction.class.php b/wcfsetup/install/files/lib/data/package/PackageAction.class.php
index ee59f60b91..bf53eda8f1 100644
--- a/wcfsetup/install/files/lib/data/package/PackageAction.class.php
+++ b/wcfsetup/install/files/lib/data/package/PackageAction.class.php
@@ -23,7 +23,7 @@ class PackageAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\package\PackageEditor';
+	protected $className = PackageEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/package/installation/plugin/PackageInstallationPluginAction.class.php b/wcfsetup/install/files/lib/data/package/installation/plugin/PackageInstallationPluginAction.class.php
index 5687693710..6d6642f78e 100644
--- a/wcfsetup/install/files/lib/data/package/installation/plugin/PackageInstallationPluginAction.class.php
+++ b/wcfsetup/install/files/lib/data/package/installation/plugin/PackageInstallationPluginAction.class.php
@@ -16,5 +16,5 @@ class PackageInstallationPluginAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\package\installation\plugin\PackageInstallationPluginEditor';
+	protected $className = PackageInstallationPluginEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/package/installation/queue/PackageInstallationQueueAction.class.php b/wcfsetup/install/files/lib/data/package/installation/queue/PackageInstallationQueueAction.class.php
index e883d95652..24055a8a01 100644
--- a/wcfsetup/install/files/lib/data/package/installation/queue/PackageInstallationQueueAction.class.php
+++ b/wcfsetup/install/files/lib/data/package/installation/queue/PackageInstallationQueueAction.class.php
@@ -21,7 +21,7 @@ class PackageInstallationQueueAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\package\installation\queue\PackageInstallationQueueEditor';
+	protected $className = PackageInstallationQueueEditor::class;
 	
 	/**
 	 * queue of the canceled installation
diff --git a/wcfsetup/install/files/lib/data/package/update/PackageUpdateAction.class.php b/wcfsetup/install/files/lib/data/package/update/PackageUpdateAction.class.php
index 8b17951e01..9f51eee7fb 100644
--- a/wcfsetup/install/files/lib/data/package/update/PackageUpdateAction.class.php
+++ b/wcfsetup/install/files/lib/data/package/update/PackageUpdateAction.class.php
@@ -3,6 +3,7 @@ namespace wcf\data\package\update;
 use wcf\data\package\installation\queue\PackageInstallationQueue;
 use wcf\data\package\installation\queue\PackageInstallationQueueEditor;
 use wcf\data\package\update\server\PackageUpdateServer;
+use wcf\data\package\update\version\PackageUpdateVersion;
 use wcf\data\package\Package;
 use wcf\data\search\Search;
 use wcf\data\search\SearchEditor;
@@ -30,7 +31,7 @@ class PackageUpdateAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\package\update\PackageUpdateEditor';
+	protected $className = PackageUpdateEditor::class;
 	
 	/**
 	 * @inheritDoc
@@ -227,8 +228,8 @@ class PackageUpdateAction extends AbstractDatabaseObjectAction {
 					continue;
 				}
 				
-				uasort($versionTypes['accessible'], ['wcf\data\package\Package', 'compareVersion']);
-				uasort($versionTypes['existing'], ['wcf\data\package\Package', 'compareVersion']);
+				uasort($versionTypes['accessible'], [Package::class, 'compareVersion']);
+				uasort($versionTypes['existing'], [Package::class, 'compareVersion']);
 				
 				$accessibleVersion = array_slice($versionTypes['accessible'], -1, 1, true);
 				$existingVersion = array_slice($versionTypes['existing'], -1, 1, true);
@@ -249,8 +250,8 @@ class PackageUpdateAction extends AbstractDatabaseObjectAction {
 				continue;
 			}
 			
-			uksort($accessible, ['wcf\data\package\Package', 'compareVersion']);
-			uksort($existing, ['wcf\data\package\Package', 'compareVersion']);
+			uksort($accessible, [Package::class, 'compareVersion']);
+			uksort($existing, [Package::class, 'compareVersion']);
 			
 			$accessible = array_pop($accessible);
 			$existing = array_pop($existing);
@@ -327,7 +328,7 @@ class PackageUpdateAction extends AbstractDatabaseObjectAction {
 		$statement = WCF::getDB()->prepareStatement($sql, 20, ($this->parameters['pageNo'] - 1) * 20);
 		$statement->execute($conditions->getParameters());
 		$packageUpdates = $packageVersionIDs = [];
-		while ($packageUpdate = $statement->fetchObject('wcf\data\package\update\PackageUpdate')) {
+		while ($packageUpdate = $statement->fetchObject(PackageUpdate::class)) {
 			$packageUpdates[$packageUpdate->packageUpdateID] = new ViewablePackageUpdate($packageUpdate);
 			
 			// collect package version ids
@@ -346,7 +347,7 @@ class PackageUpdateAction extends AbstractDatabaseObjectAction {
 		$statement = WCF::getDB()->prepareStatement($sql);
 		$statement->execute($conditions->getParameters());
 		$updateVersions = [];
-		while ($updateVersion = $statement->fetchObject('wcf\data\package\update\version\PackageUpdateVersion')) {
+		while ($updateVersion = $statement->fetchObject(PackageUpdateVersion::class)) {
 			$updateVersions[$updateVersion->packageUpdateVersionID] = $updateVersion;
 		}
 		
diff --git a/wcfsetup/install/files/lib/data/package/update/server/PackageUpdateServerAction.class.php b/wcfsetup/install/files/lib/data/package/update/server/PackageUpdateServerAction.class.php
index ef7ca93a94..e924c53f01 100644
--- a/wcfsetup/install/files/lib/data/package/update/server/PackageUpdateServerAction.class.php
+++ b/wcfsetup/install/files/lib/data/package/update/server/PackageUpdateServerAction.class.php
@@ -17,7 +17,7 @@ class PackageUpdateServerAction extends AbstractDatabaseObjectAction implements
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\package\update\server\PackageUpdateServerEditor';
+	protected $className = PackageUpdateServerEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/package/update/version/PackageUpdateVersionAction.class.php b/wcfsetup/install/files/lib/data/package/update/version/PackageUpdateVersionAction.class.php
index 0dae7d368f..9c659c659a 100644
--- a/wcfsetup/install/files/lib/data/package/update/version/PackageUpdateVersionAction.class.php
+++ b/wcfsetup/install/files/lib/data/package/update/version/PackageUpdateVersionAction.class.php
@@ -16,5 +16,5 @@ class PackageUpdateVersionAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\package\update\version\PackageUpdateVersionEditor';
+	protected $className = PackageUpdateVersionEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/poll/PollAction.class.php b/wcfsetup/install/files/lib/data/poll/PollAction.class.php
index fc63c5d361..b35417e3d6 100644
--- a/wcfsetup/install/files/lib/data/poll/PollAction.class.php
+++ b/wcfsetup/install/files/lib/data/poll/PollAction.class.php
@@ -29,7 +29,7 @@ class PollAction extends AbstractDatabaseObjectAction implements IGroupedUserLis
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\poll\PollEditor';
+	protected $className = PollEditor::class;
 	
 	/**
 	 * poll object
diff --git a/wcfsetup/install/files/lib/data/poll/option/PollOptionAction.class.php b/wcfsetup/install/files/lib/data/poll/option/PollOptionAction.class.php
index 742c2adf2d..a2b29f1042 100644
--- a/wcfsetup/install/files/lib/data/poll/option/PollOptionAction.class.php
+++ b/wcfsetup/install/files/lib/data/poll/option/PollOptionAction.class.php
@@ -16,5 +16,5 @@ class PollOptionAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\poll\option\PollOptionEditor';
+	protected $className = PollOptionEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/search/SearchAction.class.php b/wcfsetup/install/files/lib/data/search/SearchAction.class.php
index 0c56d5a71a..2d0b21206e 100644
--- a/wcfsetup/install/files/lib/data/search/SearchAction.class.php
+++ b/wcfsetup/install/files/lib/data/search/SearchAction.class.php
@@ -16,5 +16,5 @@ class SearchAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\search\SearchEditor';
+	protected $className = SearchEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/search/keyword/SearchKeywordAction.class.php b/wcfsetup/install/files/lib/data/search/keyword/SearchKeywordAction.class.php
index f0b7477220..4e81403e51 100644
--- a/wcfsetup/install/files/lib/data/search/keyword/SearchKeywordAction.class.php
+++ b/wcfsetup/install/files/lib/data/search/keyword/SearchKeywordAction.class.php
@@ -18,7 +18,7 @@ class SearchKeywordAction extends AbstractDatabaseObjectAction implements ISearc
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\search\keyword\SearchKeywordEditor';
+	protected $className = SearchKeywordEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/session/SessionAction.class.php b/wcfsetup/install/files/lib/data/session/SessionAction.class.php
index f1eeb518e0..5358760c51 100644
--- a/wcfsetup/install/files/lib/data/session/SessionAction.class.php
+++ b/wcfsetup/install/files/lib/data/session/SessionAction.class.php
@@ -25,7 +25,7 @@ class SessionAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\session\SessionEditor';
+	protected $className = SessionEditor::class;
 	
 	/**
 	 * list of data values returned upon a keep alive request
diff --git a/wcfsetup/install/files/lib/data/sitemap/Sitemap.class.php b/wcfsetup/install/files/lib/data/sitemap/Sitemap.class.php
index 1c863170ca..7868b2c1a5 100644
--- a/wcfsetup/install/files/lib/data/sitemap/Sitemap.class.php
+++ b/wcfsetup/install/files/lib/data/sitemap/Sitemap.class.php
@@ -4,6 +4,7 @@ use wcf\data\DatabaseObject;
 use wcf\data\TDatabaseObjectOptions;
 use wcf\data\TDatabaseObjectPermissions;
 use wcf\system\exception\SystemException;
+use wcf\system\sitemap\ISitemapProvider;
 
 /**
  * Represents a sitemap entry.
@@ -56,8 +57,8 @@ class Sitemap extends DatabaseObject {
 				throw new SystemException("Unable to find class '".$this->className."' for sitemap '".$this->sitemapName."'");
 			}
 			
-			if (!is_subclass_of($this->className, 'wcf\system\sitemap\ISitemapProvider')) {
-				throw new SystemException("'".$this->className."' does not implement 'wcf\system\sitemap\ISitemapProvider'");
+			if (!is_subclass_of($this->className, ISitemapProvider::class)) {
+				throw new SystemException("'".$this->className."' does not implement '".ISitemapProvider::class."'");
 			}
 			
 			$this->sitemapObj = new $this->className();
diff --git a/wcfsetup/install/files/lib/data/smiley/SmileyAction.class.php b/wcfsetup/install/files/lib/data/smiley/SmileyAction.class.php
index 154efe149a..4105973227 100644
--- a/wcfsetup/install/files/lib/data/smiley/SmileyAction.class.php
+++ b/wcfsetup/install/files/lib/data/smiley/SmileyAction.class.php
@@ -20,7 +20,7 @@ class SmileyAction extends AbstractDatabaseObjectAction implements ISortableActi
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\smiley\SmileyEditor';
+	protected $className = SmileyEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/smiley/category/SmileyCategoryAction.class.php b/wcfsetup/install/files/lib/data/smiley/category/SmileyCategoryAction.class.php
index 5e0a5e88b7..2a442fd577 100644
--- a/wcfsetup/install/files/lib/data/smiley/category/SmileyCategoryAction.class.php
+++ b/wcfsetup/install/files/lib/data/smiley/category/SmileyCategoryAction.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\data\smiley\category;
+use wcf\data\category\CategoryEditor;
 use wcf\data\AbstractDatabaseObjectAction;
 use wcf\system\exception\IllegalLinkException;
 use wcf\system\WCF;
@@ -18,7 +19,7 @@ class SmileyCategoryAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\category\CategoryEditor';
+	protected $className = CategoryEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/spider/SpiderAction.class.php b/wcfsetup/install/files/lib/data/spider/SpiderAction.class.php
index 88e32228b9..0999c04ddf 100644
--- a/wcfsetup/install/files/lib/data/spider/SpiderAction.class.php
+++ b/wcfsetup/install/files/lib/data/spider/SpiderAction.class.php
@@ -16,5 +16,5 @@ class SpiderAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\spider\SpiderEditor';
+	protected $className = SpiderEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/stat/daily/StatDailyAction.class.php b/wcfsetup/install/files/lib/data/stat/daily/StatDailyAction.class.php
index 344c09aa22..668d6af3fd 100644
--- a/wcfsetup/install/files/lib/data/stat/daily/StatDailyAction.class.php
+++ b/wcfsetup/install/files/lib/data/stat/daily/StatDailyAction.class.php
@@ -20,7 +20,7 @@ class StatDailyAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\stat\daily\StatDailyEditor';
+	protected $className = StatDailyEditor::class;
 	
 	/**
 	 * Validates the getData action.
diff --git a/wcfsetup/install/files/lib/data/style/StyleAction.class.php b/wcfsetup/install/files/lib/data/style/StyleAction.class.php
index e8620110aa..394be29d25 100644
--- a/wcfsetup/install/files/lib/data/style/StyleAction.class.php
+++ b/wcfsetup/install/files/lib/data/style/StyleAction.class.php
@@ -35,7 +35,7 @@ class StyleAction extends AbstractDatabaseObjectAction implements IToggleAction,
 	/**
 	 * @inheritdoc
 	 */
-	protected $className = 'wcf\data\style\StyleEditor';
+	protected $className = StyleEditor::class;
 	
 	/**
 	 * @inheritdoc
diff --git a/wcfsetup/install/files/lib/data/style/StyleEditor.class.php b/wcfsetup/install/files/lib/data/style/StyleEditor.class.php
index 2f55bd42a8..0f1c17c00d 100644
--- a/wcfsetup/install/files/lib/data/style/StyleEditor.class.php
+++ b/wcfsetup/install/files/lib/data/style/StyleEditor.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\data\style;
+use wcf\data\language\category\LanguageCategory;
 use wcf\data\language\LanguageList;
 use wcf\data\package\Package;
 use wcf\data\package\PackageCache;
@@ -559,7 +560,7 @@ class StyleEditor extends DatabaseObjectEditor implements IEditableCachedObject
 				WHERE	languageCategory = ?";
 			$statement2 = WCF::getDB()->prepareStatement($sql);
 			$statement2->execute(['wcf.style']);
-			$languageCategory = $statement2->fetchObject('wcf\data\language\category\LanguageCategory');
+			$languageCategory = $statement2->fetchObject(LanguageCategory::class);
 		}
 		else {
 			$languageCategory = LanguageFactory::getInstance()->getCategory('wcf.style');
diff --git a/wcfsetup/install/files/lib/data/style/variable/StyleVariableAction.class.php b/wcfsetup/install/files/lib/data/style/variable/StyleVariableAction.class.php
index 005f5b01c0..f72361a3ff 100644
--- a/wcfsetup/install/files/lib/data/style/variable/StyleVariableAction.class.php
+++ b/wcfsetup/install/files/lib/data/style/variable/StyleVariableAction.class.php
@@ -16,5 +16,5 @@ class StyleVariableAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\style\variable\StyleVariableEditor';
+	protected $className = StyleVariableEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/tag/TagAction.class.php b/wcfsetup/install/files/lib/data/tag/TagAction.class.php
index 2f34bb17ad..e62954cf89 100644
--- a/wcfsetup/install/files/lib/data/tag/TagAction.class.php
+++ b/wcfsetup/install/files/lib/data/tag/TagAction.class.php
@@ -26,7 +26,7 @@ class TagAction extends AbstractDatabaseObjectAction implements ISearchAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\tag\TagEditor';
+	protected $className = TagEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/template/TemplateAction.class.php b/wcfsetup/install/files/lib/data/template/TemplateAction.class.php
index 77910aff9e..e2c7a1bd21 100644
--- a/wcfsetup/install/files/lib/data/template/TemplateAction.class.php
+++ b/wcfsetup/install/files/lib/data/template/TemplateAction.class.php
@@ -17,7 +17,7 @@ class TemplateAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\template\TemplateEditor';
+	protected $className = TemplateEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/template/TemplateList.class.php b/wcfsetup/install/files/lib/data/template/TemplateList.class.php
index e5ad95bbc4..7ffcb30073 100644
--- a/wcfsetup/install/files/lib/data/template/TemplateList.class.php
+++ b/wcfsetup/install/files/lib/data/template/TemplateList.class.php
@@ -18,7 +18,7 @@ class TemplateList extends DatabaseObjectList {
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\template\Template';
+	public $className = Template::class;
 	
 	/**
 	 * Creates a new TemplateList object.
diff --git a/wcfsetup/install/files/lib/data/template/group/TemplateGroupAction.class.php b/wcfsetup/install/files/lib/data/template/group/TemplateGroupAction.class.php
index 7bccd08e0c..a1a31256d9 100644
--- a/wcfsetup/install/files/lib/data/template/group/TemplateGroupAction.class.php
+++ b/wcfsetup/install/files/lib/data/template/group/TemplateGroupAction.class.php
@@ -16,7 +16,7 @@ class TemplateGroupAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\template\group\TemplateGroupEditor';
+	protected $className = TemplateGroupEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/template/listener/TemplateListenerAction.class.php b/wcfsetup/install/files/lib/data/template/listener/TemplateListenerAction.class.php
index 073d82a6b1..2ece26cb4b 100644
--- a/wcfsetup/install/files/lib/data/template/listener/TemplateListenerAction.class.php
+++ b/wcfsetup/install/files/lib/data/template/listener/TemplateListenerAction.class.php
@@ -16,5 +16,5 @@ class TemplateListenerAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\template\listener\TemplateListenerEditor';
+	protected $className = TemplateListenerEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/user/follow/UserFollowingAction.class.php b/wcfsetup/install/files/lib/data/user/follow/UserFollowingAction.class.php
index 0646cb3fb8..cb4fa4714e 100644
--- a/wcfsetup/install/files/lib/data/user/follow/UserFollowingAction.class.php
+++ b/wcfsetup/install/files/lib/data/user/follow/UserFollowingAction.class.php
@@ -19,7 +19,7 @@ class UserFollowingAction extends UserFollowAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\user\follow\UserFollowEditor';
+	protected $className = UserFollowEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/user/group/UserGroupAction.class.php b/wcfsetup/install/files/lib/data/user/group/UserGroupAction.class.php
index 1da52ece5a..154576c727 100644
--- a/wcfsetup/install/files/lib/data/user/group/UserGroupAction.class.php
+++ b/wcfsetup/install/files/lib/data/user/group/UserGroupAction.class.php
@@ -21,7 +21,7 @@ class UserGroupAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\user\group\UserGroupEditor';
+	public $className = UserGroupEditor::class;
 	
 	/**
 	 * editor object for the copied user group
diff --git a/wcfsetup/install/files/lib/data/user/group/option/UserGroupOptionAction.class.php b/wcfsetup/install/files/lib/data/user/group/option/UserGroupOptionAction.class.php
index 3e61654dd1..c729d0ad17 100644
--- a/wcfsetup/install/files/lib/data/user/group/option/UserGroupOptionAction.class.php
+++ b/wcfsetup/install/files/lib/data/user/group/option/UserGroupOptionAction.class.php
@@ -18,7 +18,7 @@ class UserGroupOptionAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\user\group\option\UserGroupOptionEditor';
+	protected $className = UserGroupOptionEditor::class;
 	
 	/**
 	 * Updates option values for given option id.
diff --git a/wcfsetup/install/files/lib/data/user/group/option/category/UserGroupOptionCategoryAction.class.php b/wcfsetup/install/files/lib/data/user/group/option/category/UserGroupOptionCategoryAction.class.php
index 1349a37f7f..766c160c52 100644
--- a/wcfsetup/install/files/lib/data/user/group/option/category/UserGroupOptionCategoryAction.class.php
+++ b/wcfsetup/install/files/lib/data/user/group/option/category/UserGroupOptionCategoryAction.class.php
@@ -16,5 +16,5 @@ class UserGroupOptionCategoryAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\user\group\option\category\UserGroupOptionCategoryEditor';
+	protected $className = UserGroupOptionCategoryEditor::class;
 }
diff --git a/wcfsetup/install/files/lib/data/user/ignore/ViewableUserIgnoreList.class.php b/wcfsetup/install/files/lib/data/user/ignore/ViewableUserIgnoreList.class.php
index 3d3f6d5af7..4959be4648 100644
--- a/wcfsetup/install/files/lib/data/user/ignore/ViewableUserIgnoreList.class.php
+++ b/wcfsetup/install/files/lib/data/user/ignore/ViewableUserIgnoreList.class.php
@@ -1,5 +1,7 @@
 <?php
 namespace wcf\data\user\ignore;
+use wcf\data\user\User;
+use wcf\data\user\UserProfile;
 
 /**
  * Represents a list of ignored users.
@@ -15,17 +17,17 @@ class ViewableUserIgnoreList extends UserIgnoreList {
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\user\ignore\UserIgnore';
+	public $className = UserIgnore::class;
 	
 	/**
 	 * @inheritDoc
 	 */
-	public $decoratorClassName = 'wcf\data\user\UserProfile';
+	public $decoratorClassName = UserProfile::class;
 	
 	/**
 	 * @inheritDoc
 	 */
-	public $objectClassName = 'wcf\data\user\User';
+	public $objectClassName = User::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/user/menu/item/UserMenuItem.class.php b/wcfsetup/install/files/lib/data/user/menu/item/UserMenuItem.class.php
index 0c1776e922..8ded1793cb 100644
--- a/wcfsetup/install/files/lib/data/user/menu/item/UserMenuItem.class.php
+++ b/wcfsetup/install/files/lib/data/user/menu/item/UserMenuItem.class.php
@@ -2,6 +2,7 @@
 namespace wcf\data\user\menu\item;
 use wcf\data\ProcessibleDatabaseObject;
 use wcf\system\menu\user\DefaultUserMenuItemProvider;
+use wcf\system\menu\user\IUserMenuItemProvider;
 use wcf\system\menu\ITreeMenuItem;
 use wcf\system\request\LinkHandler;
 use wcf\system\Regex;
@@ -43,7 +44,7 @@ class UserMenuItem extends ProcessibleDatabaseObject implements ITreeMenuItem {
 	/**
 	 * @inheritDoc
 	 */
-	protected static $processorInterface = 'wcf\system\menu\user\IUserMenuItemProvider';
+	protected static $processorInterface = IUserMenuItemProvider::class;
 	
 	/**
 	 * application abbreviation
diff --git a/wcfsetup/install/files/lib/data/user/notification/event/UserNotificationEvent.class.php b/wcfsetup/install/files/lib/data/user/notification/event/UserNotificationEvent.class.php
index 9bcbb8b564..e31d3ac960 100644
--- a/wcfsetup/install/files/lib/data/user/notification/event/UserNotificationEvent.class.php
+++ b/wcfsetup/install/files/lib/data/user/notification/event/UserNotificationEvent.class.php
@@ -3,6 +3,7 @@ namespace wcf\data\user\notification\event;
 use wcf\data\ProcessibleDatabaseObject;
 use wcf\data\TDatabaseObjectOptions;
 use wcf\data\TDatabaseObjectPermissions;
+use wcf\system\user\notification\event\IUserNotificationEvent;
 
 /**
  * Represents a user notification event.
@@ -41,5 +42,5 @@ class UserNotificationEvent extends ProcessibleDatabaseObject {
 	/**
 	 * @inheritDoc
 	 */
-	protected static $processorInterface = 'wcf\system\user\notification\event\IUserNotificationEvent';
+	protected static $processorInterface = IUserNotificationEvent::class;
 }
diff --git a/wcfsetup/install/files/lib/data/user/option/UserOptionAction.class.php b/wcfsetup/install/files/lib/data/user/option/UserOptionAction.class.php
index 385568e5e3..15ae734a47 100644
--- a/wcfsetup/install/files/lib/data/user/option/UserOptionAction.class.php
+++ b/wcfsetup/install/files/lib/data/user/option/UserOptionAction.class.php
@@ -18,7 +18,7 @@ class UserOptionAction extends AbstractDatabaseObjectAction implements IToggleAc
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\user\option\UserOptionEditor';
+	protected $className = UserOptionEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/user/option/category/UserOptionCategoryAction.class.php b/wcfsetup/install/files/lib/data/user/option/category/UserOptionCategoryAction.class.php
index 38bf144ab4..95e0385eff 100644
--- a/wcfsetup/install/files/lib/data/user/option/category/UserOptionCategoryAction.class.php
+++ b/wcfsetup/install/files/lib/data/user/option/category/UserOptionCategoryAction.class.php
@@ -16,7 +16,7 @@ class UserOptionCategoryAction extends AbstractDatabaseObjectAction {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\user\option\category\UserOptionCategoryEditor';
+	protected $className = UserOptionCategoryEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/data/user/profile/menu/item/UserProfileMenuItem.class.php b/wcfsetup/install/files/lib/data/user/profile/menu/item/UserProfileMenuItem.class.php
index 8d195b2d2c..aba58b66ae 100644
--- a/wcfsetup/install/files/lib/data/user/profile/menu/item/UserProfileMenuItem.class.php
+++ b/wcfsetup/install/files/lib/data/user/profile/menu/item/UserProfileMenuItem.class.php
@@ -67,11 +67,11 @@ class UserProfileMenuItem extends DatabaseObject {
 			}
 			
 			if (!is_subclass_of($this->className, SingletonFactory::class)) {
-				throw new SystemException("'".$this->className."' does not extend 'wcf\system\SingletonFactory'");
+				throw new SystemException("'".$this->className."' does not extend '".SingletonFactory::class."'");
 			}
 			
 			if (!is_subclass_of($this->className, IUserProfileMenuContent::class)) {
-				throw new SystemException("'".$this->className."' does not implement 'wcf\system\menu\user\profile\content\IUserProfileMenuContent'");
+				throw new SystemException("'".$this->className."' does not implement '".IUserProfileMenuContent::class."'");
 			}
 			
 			$this->contentManager = call_user_func([$this->className, 'getInstance']);
diff --git a/wcfsetup/install/files/lib/page/FollowingPage.class.php b/wcfsetup/install/files/lib/page/FollowingPage.class.php
index d296064ff8..fe3796a3bc 100644
--- a/wcfsetup/install/files/lib/page/FollowingPage.class.php
+++ b/wcfsetup/install/files/lib/page/FollowingPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\page;
+use wcf\data\user\follow\UserFollowingList;
 use wcf\system\menu\user\UserMenu;
 use wcf\system\WCF;
 
@@ -22,7 +23,7 @@ class FollowingPage extends MultipleLinkPage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\user\follow\UserFollowingList';
+	public $objectListClassName = UserFollowingList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/page/IgnoredUsersPage.class.php b/wcfsetup/install/files/lib/page/IgnoredUsersPage.class.php
index a8fb335102..c59343defa 100644
--- a/wcfsetup/install/files/lib/page/IgnoredUsersPage.class.php
+++ b/wcfsetup/install/files/lib/page/IgnoredUsersPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\page;
+use wcf\data\user\ignore\ViewableUserIgnoreList;
 use wcf\system\menu\user\UserMenu;
 use wcf\system\WCF;
 
@@ -22,7 +23,7 @@ class IgnoredUsersPage extends MultipleLinkPage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\user\ignore\ViewableUserIgnoreList';
+	public $objectListClassName = ViewableUserIgnoreList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/page/MembersListPage.class.php b/wcfsetup/install/files/lib/page/MembersListPage.class.php
index 99fbd24681..4f405cb216 100644
--- a/wcfsetup/install/files/lib/page/MembersListPage.class.php
+++ b/wcfsetup/install/files/lib/page/MembersListPage.class.php
@@ -2,6 +2,7 @@
 namespace wcf\page;
 use wcf\data\search\Search;
 use wcf\data\user\User;
+use wcf\data\user\UserProfileList;
 use wcf\system\database\PostgreSQLDatabase;
 use wcf\system\exception\IllegalLinkException;
 use wcf\system\request\LinkHandler;
@@ -64,7 +65,7 @@ class MembersListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\user\UserProfileList';
+	public $objectListClassName = UserProfileList::class;
 	
 	/**
 	 * letter
diff --git a/wcfsetup/install/files/lib/page/ModerationListPage.class.php b/wcfsetup/install/files/lib/page/ModerationListPage.class.php
index d57aa6a31e..c7b3a7aec7 100644
--- a/wcfsetup/install/files/lib/page/ModerationListPage.class.php
+++ b/wcfsetup/install/files/lib/page/ModerationListPage.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\page;
 use wcf\data\moderation\queue\ModerationQueue;
+use wcf\data\moderation\queue\ViewableModerationQueueList;
 use wcf\system\exception\IllegalLinkException;
 use wcf\system\moderation\queue\ModerationQueueManager;
 use wcf\system\WCF;
@@ -57,7 +58,7 @@ class ModerationListPage extends SortablePage {
 	/**
 	 * @inheritDoc
 	 */
-	public $objectListClassName = 'wcf\data\moderation\queue\ViewableModerationQueueList';
+	public $objectListClassName = ViewableModerationQueueList::class;
 	
 	/**
 	 * status bit
diff --git a/wcfsetup/install/files/lib/page/MultipleLinkPage.class.php b/wcfsetup/install/files/lib/page/MultipleLinkPage.class.php
index b071f888bf..277ce1c45e 100644
--- a/wcfsetup/install/files/lib/page/MultipleLinkPage.class.php
+++ b/wcfsetup/install/files/lib/page/MultipleLinkPage.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\page;
+use wcf\data\DatabaseObjectList;
 use wcf\system\event\EventHandler;
 use wcf\system\exception\SystemException;
 use wcf\system\WCF;
@@ -138,8 +139,8 @@ abstract class MultipleLinkPage extends AbstractPage {
 			throw new SystemException('DatabaseObjectList class name not specified.');
 		}
 		
-		if (!is_subclass_of($this->objectListClassName, 'wcf\data\DatabaseObjectList')) {
-			throw new SystemException("'".$this->objectListClassName."' does not extend 'wcf\data\DatabaseObjectList'");
+		if (!is_subclass_of($this->objectListClassName, DatabaseObjectList::class)) {
+			throw new SystemException("'".$this->objectListClassName."' does not extend '".DatabaseObjectList::class."'");
 		}
 		
 		$this->objectList = new $this->objectListClassName();
diff --git a/wcfsetup/install/files/lib/page/SearchResultPage.class.php b/wcfsetup/install/files/lib/page/SearchResultPage.class.php
index 09c3799f1f..7c95ef4548 100644
--- a/wcfsetup/install/files/lib/page/SearchResultPage.class.php
+++ b/wcfsetup/install/files/lib/page/SearchResultPage.class.php
@@ -142,7 +142,7 @@ class SearchResultPage extends MultipleLinkPage {
 			$objectType = SearchEngine::getInstance()->getObjectType($type);
 			if (($message = $objectType->getObject($objectID)) !== null) {
 				if (!($message instanceof ISearchResultObject)) {
-					throw new SystemException("'".get_class($message)."' does not implement 'wcf\data\search\ISearchResultObject'");
+					throw new SystemException("'".get_class($message)."' does not implement '".ISearchResultObject::class."'");
 				}
 				
 				$this->messages[] = $message;
diff --git a/wcfsetup/install/files/lib/system/CLIWCF.class.php b/wcfsetup/install/files/lib/system/CLIWCF.class.php
index 1aa7cee0e3..ee6d601a2a 100644
--- a/wcfsetup/install/files/lib/system/CLIWCF.class.php
+++ b/wcfsetup/install/files/lib/system/CLIWCF.class.php
@@ -22,7 +22,7 @@ use Zend\Console\Getopt as ArgvParser;
 use Zend\Loader\StandardAutoloader as ZendLoader;
 
 // set exception handler
-set_exception_handler(['wcf\system\CLIWCF', 'handleCLIException']);
+set_exception_handler([CLIWCF::class, 'handleCLIException']);
 
 /**
  * Extends WCF class with functions for CLI.
@@ -83,7 +83,7 @@ class CLIWCF extends WCF {
 		$this->initApplications();
 		
 		// the destructor registered in core.functions.php will only call the destructor of the parent class
-		register_shutdown_function(['wcf\system\CLIWCF', 'destruct']);
+		register_shutdown_function([self::class, 'destruct']);
 		
 		$this->initArgv();
 		$this->initPHPLine();
diff --git a/wcfsetup/install/files/lib/system/WCF.class.php b/wcfsetup/install/files/lib/system/WCF.class.php
index 6323ab85f9..2fc6c4dceb 100644
--- a/wcfsetup/install/files/lib/system/WCF.class.php
+++ b/wcfsetup/install/files/lib/system/WCF.class.php
@@ -14,6 +14,7 @@ use wcf\system\box\BoxHandler;
 use wcf\system\cache\builder\CoreObjectCacheBuilder;
 use wcf\system\cache\builder\PackageUpdateCacheBuilder;
 use wcf\system\cronjob\CronjobScheduler;
+use wcf\system\database\MySQLDatabase;
 use wcf\system\event\EventHandler;
 use wcf\system\exception\AJAXException;
 use wcf\system\exception\ErrorException;
@@ -299,7 +300,7 @@ class WCF {
 		// get configuration
 		$dbHost = $dbUser = $dbPassword = $dbName = '';
 		$dbPort = 0;
-		$dbClass = 'wcf\system\database\MySQLDatabase';
+		$dbClass = MySQLDatabase::class;
 		require(WCF_DIR.'config.inc.php');
 		
 		// create database connection
@@ -528,7 +529,7 @@ class WCF {
 		self::$autoloadDirectories[$abbreviation] = $packageDir . 'lib/';
 		
 		$className = $abbreviation.'\system\\'.strtoupper($abbreviation).'Core';
-		if (class_exists($className) && is_subclass_of($className, 'wcf\system\application\IApplication')) {
+		if (class_exists($className) && is_subclass_of($className, IApplication::class)) {
 			// include config file
 			$configPath = $packageDir . PackageInstallationDispatcher::CONFIG_FILE;
 			
@@ -556,7 +557,7 @@ class WCF {
 		}
 		else {
 			unset(self::$autoloadDirectories[$abbreviation]);
-			throw new SystemException("Unable to run '".$package->package."', '".$className."' is missing or does not implement 'wcf\system\application\IApplication'.");
+			throw new SystemException("Unable to run '".$package->package."', '".$className."' is missing or does not implement '".IApplication::class."'.");
 		}
 		
 		// register template path in ACP
@@ -719,8 +720,8 @@ class WCF {
 		}
 		
 		if (class_exists($objectName)) {
-			if (!(is_subclass_of($objectName, 'wcf\system\SingletonFactory'))) {
-				throw new SystemException("class '".$objectName."' does not implement the interface 'SingletonFactory'");
+			if (!(is_subclass_of($objectName, SingletonFactory::class))) {
+				throw new SystemException("class '".$objectName."' does not implement the interface '".SingletonFactory::class."'");
 			}
 			
 			self::$coreObject[$className] = call_user_func([$objectName, 'getInstance']);
diff --git a/wcfsetup/install/files/lib/system/WCFSetup.class.php b/wcfsetup/install/files/lib/system/WCFSetup.class.php
index a9950efbc2..6ac9a25fbe 100644
--- a/wcfsetup/install/files/lib/system/WCFSetup.class.php
+++ b/wcfsetup/install/files/lib/system/WCFSetup.class.php
@@ -8,6 +8,7 @@ use wcf\data\user\User;
 use wcf\data\user\UserAction;
 use wcf\system\cache\builder\LanguageCacheBuilder;
 use wcf\system\database\util\SQLParser;
+use wcf\system\database\MySQLDatabase;
 use wcf\system\exception\SystemException;
 use wcf\system\exception\UserInputException;
 use wcf\system\io\File;
@@ -93,7 +94,7 @@ class WCFSetup extends WCF {
 	 * @var	string[][]
 	 */
 	protected static $dbClasses = [
-		'MySQLDatabase' => ['class' => 'wcf\system\database\MySQLDatabase', 'minversion' => '5.1.17']//,		// MySQL 5.1.17+
+		'MySQLDatabase' => ['class' => MySQLDatabase::class, 'minversion' => '5.1.17']//,		// MySQL 5.1.17+
 		//'PostgreSQLDatabase' => ['class' => 'wcf\system\database\PostgreSQLDatabase', 'minversion' => '8.2.0']	// PostgreSQL 8.2.0+
 	];
 	
@@ -709,7 +710,7 @@ class WCFSetup extends WCF {
 					}
 				}
 				// check innodb support
-				if ($dbClass == 'wcf\system\database\MySQLDatabase') {
+				if ($dbClass == MySQLDatabase::class) {
 					$sql = "SHOW ENGINES";
 					$statement = $db->prepareStatement($sql);
 					$statement->execute();
diff --git a/wcfsetup/install/files/lib/system/application/AbstractApplication.class.php b/wcfsetup/install/files/lib/system/application/AbstractApplication.class.php
index 115ed87dcb..7559bae07f 100644
--- a/wcfsetup/install/files/lib/system/application/AbstractApplication.class.php
+++ b/wcfsetup/install/files/lib/system/application/AbstractApplication.class.php
@@ -3,6 +3,7 @@ namespace wcf\system\application;
 use wcf\data\package\PackageCache;
 use wcf\system\exception\SystemException;
 use wcf\system\SingletonFactory;
+use wcf\system\WCF;
 
 /**
  * Abstract implementation of a community framework application.
@@ -98,6 +99,6 @@ abstract class AbstractApplication extends SingletonFactory implements IApplicat
 	 * @inheritDoc
 	 */
 	public static function __callStatic($method, array $arguments) {
-		return call_user_func_array(['wcf\system\WCF', $method], $arguments);
+		return call_user_func_array([WCF::class, $method], $arguments);
 	}
 }
diff --git a/wcfsetup/install/files/lib/system/background/BackgroundQueueHandler.class.php b/wcfsetup/install/files/lib/system/background/BackgroundQueueHandler.class.php
index bf3d31c75f..2f417ceb5c 100644
--- a/wcfsetup/install/files/lib/system/background/BackgroundQueueHandler.class.php
+++ b/wcfsetup/install/files/lib/system/background/BackgroundQueueHandler.class.php
@@ -57,7 +57,7 @@ class BackgroundQueueHandler extends SingletonFactory {
 		if (!is_array($jobs)) $jobs = [$jobs];
 		foreach ($jobs as $job) {
 			if (!($job instanceof AbstractBackgroundJob)) {
-				throw new SystemException('$jobs contains an item that does not extend \wcf\system\background\job\AbstractBackgroundJob.');
+				throw new SystemException('$jobs contains an item that does not extend \''.AbstractBackgroundJob::class.'\'.');
 			}
 		}
 		
diff --git a/wcfsetup/install/files/lib/system/bbcode/CodeBBCode.class.php b/wcfsetup/install/files/lib/system/bbcode/CodeBBCode.class.php
index 024c474a9c..a6c15eaa40 100644
--- a/wcfsetup/install/files/lib/system/bbcode/CodeBBCode.class.php
+++ b/wcfsetup/install/files/lib/system/bbcode/CodeBBCode.class.php
@@ -1,5 +1,19 @@
 <?php
 namespace wcf\system\bbcode;
+use wcf\system\bbcode\highlighter\BashHighlighter;
+use wcf\system\bbcode\highlighter\BrainfuckHighlighter;
+use wcf\system\bbcode\highlighter\CHighlighter;
+use wcf\system\bbcode\highlighter\DiffHighlighter;
+use wcf\system\bbcode\highlighter\HtmlHighlighter;
+use wcf\system\bbcode\highlighter\JavaHighlighter;
+use wcf\system\bbcode\highlighter\JsHighlighter;
+use wcf\system\bbcode\highlighter\PerlHighlighter;
+use wcf\system\bbcode\highlighter\PhpHighlighter;
+use wcf\system\bbcode\highlighter\PlainHighlighter;
+use wcf\system\bbcode\highlighter\PythonHighlighter;
+use wcf\system\bbcode\highlighter\SqlHighlighter;
+use wcf\system\bbcode\highlighter\TexHighlighter;
+use wcf\system\bbcode\highlighter\XmlHighlighter;
 use wcf\system\Regex;
 use wcf\system\WCF;
 use wcf\util\StringUtil;
@@ -50,7 +64,7 @@ class CodeBBCode extends AbstractBBCode {
 		$this->mapAttributes($openingTag);
 		
 		// fetch highlighter-classname
-		$className = '\wcf\system\bbcode\highlighter\PlainHighlighter';
+		$className = PlainHighlighter::class;
 		
 		// no highlighting for strings over a certain size, to prevent DoS
 		// this serves as a safety net in case one of the regular expressions
@@ -61,70 +75,70 @@ class CodeBBCode extends AbstractBBCode {
 				
 				switch (mb_substr($className, strlen('\wcf\system\bbcode\highlighter\\'))) {
 					case 'ShellHighlighter':
-						$className = '\wcf\system\bbcode\highlighter\BashHighlighter';
+						$className = BashHighlighter::class;
 					break;
 					
 					case 'C++Highlighter':
-						$className = '\wcf\system\bbcode\highlighter\CHighlighter';
+						$className = CHighlighter::class;
 					break;
 					
 					case 'JavascriptHighlighter':
-						$className = '\wcf\system\bbcode\highlighter\JsHighlighter';
+						$className = JsHighlighter::class;
 					break;
 					
 					case 'LatexHighlighter':
-						$className = '\wcf\system\bbcode\highlighter\TexHighlighter';
+						$className = TexHighlighter::class;
 					break;
 				}
 			}
 			else {
 				// try to guess highlighter
 				if (mb_strpos($content, '<?php') !== false) {
-					$className = '\wcf\system\bbcode\highlighter\PhpHighlighter';
+					$className = PhpHighlighter::class;
 				}
 				else if (mb_strpos($content, '<html') !== false) {
-					$className = '\wcf\system\bbcode\highlighter\HtmlHighlighter';
+					$className = HtmlHighlighter::class;
 				}
 				else if (mb_strpos($content, '<?xml') === 0) {
-					$className = '\wcf\system\bbcode\highlighter\XmlHighlighter';
+					$className = XmlHighlighter::class;
 				}
 				else if (	mb_strpos($content, 'SELECT') === 0
 						||	mb_strpos($content, 'UPDATE') === 0
 						||	mb_strpos($content, 'INSERT') === 0
 						||	mb_strpos($content, 'DELETE') === 0) {
-					$className = '\wcf\system\bbcode\highlighter\SqlHighlighter';
+					$className = SqlHighlighter::class;
 				}
 				else if (mb_strpos($content, 'import java.') !== false) {
-					$className = '\wcf\system\bbcode\highlighter\JavaHighlighter';
+					$className = JavaHighlighter::class;
 				}
 				else if (	mb_strpos($content, "---") !== false
 						&&	mb_strpos($content, "\n+++") !== false) {
-					$className = '\wcf\system\bbcode\highlighter\DiffHighlighter';
+					$className = DiffHighlighter::class;
 				}
 				else if (mb_strpos($content, "\n#include ") !== false) {
-					$className = '\wcf\system\bbcode\highlighter\CHighlighter';
+					$className = CHighlighter::class;
 				}
 				else if (mb_strpos($content, '#!/usr/bin/perl') === 0) {
-					$className = '\wcf\system\bbcode\highlighter\PerlHighlighter';
+					$className = PerlHighlighter::class;
 				}
 				else if (mb_strpos($content, 'def __init__(self') !== false) {
-					$className = '\wcf\system\bbcode\highlighter\PythonHighlighter';
+					$className = PythonHighlighter::class;
 				}
 				else if (Regex::compile('^#!/bin/(ba|z)?sh')->match($content)) {
-					$className = '\wcf\system\bbcode\highlighter\BashHighlighter';
+					$className = BashHighlighter::class;
 				}
 				else if (mb_strpos($content, '\\documentclass') !== false) {
-					$className = '\wcf\system\bbcode\highlighter\TexHighlighter';
+					$className = TexHighlighter::class;
 				}
 				else if (Regex::compile('[-\\+\\.,\\[\\]\\>\\<]{9}')->match($content)) {
 					// 9 times a brainfuck char in a row -> seems to be brainfuck
-					$className = '\wcf\system\bbcode\highlighter\BrainfuckHighlighter';
+					$className = BrainfuckHighlighter::class;
 				}
 			}
 		}
 		
 		if (!class_exists($className)) {
-			$className = '\wcf\system\bbcode\highlighter\PlainHighlighter';
+			$className = PlainHighlighter::class;
 		}
 		
 		if ($parser->getOutputType() == 'text/html') {
diff --git a/wcfsetup/install/files/lib/system/cache/builder/ACPMenuCacheBuilder.class.php b/wcfsetup/install/files/lib/system/cache/builder/ACPMenuCacheBuilder.class.php
index e910f512ed..d4fd5b5745 100644
--- a/wcfsetup/install/files/lib/system/cache/builder/ACPMenuCacheBuilder.class.php
+++ b/wcfsetup/install/files/lib/system/cache/builder/ACPMenuCacheBuilder.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\cache\builder;
+use wcf\acp\form\OptionForm;
 use wcf\data\acp\menu\item\ACPMenuItem;
 use wcf\data\acp\menu\item\ACPMenuItemList;
 use wcf\data\option\category\OptionCategory;
@@ -49,7 +50,7 @@ class ACPMenuCacheBuilder extends AbstractCacheBuilder {
 			$data['wcf.acp.menu.link.option.category'][] = new ACPMenuItem(null, [
 				'menuItem' => 'wcf.acp.option.category.'.$optionCategory->categoryName,
 				'parentMenuItem' => 'wcf.acp.menu.link.option.category',
-				'menuItemController' => 'wcf\acp\form\OptionForm',
+				'menuItemController' => OptionForm::class,
 				'permissions' => $optionCategory->permissions,
 				'optionCategoryID' => $optionCategory->categoryID,
 				'options' => $optionCategory->options
diff --git a/wcfsetup/install/files/lib/system/cache/builder/EventListenerCacheBuilder.class.php b/wcfsetup/install/files/lib/system/cache/builder/EventListenerCacheBuilder.class.php
index 29119e7579..c7acb9adb7 100644
--- a/wcfsetup/install/files/lib/system/cache/builder/EventListenerCacheBuilder.class.php
+++ b/wcfsetup/install/files/lib/system/cache/builder/EventListenerCacheBuilder.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\cache\builder;
+use wcf\data\event\listener\EventListener;
 use wcf\system\event\EventHandler;
 use wcf\system\WCF;
 
@@ -36,7 +37,7 @@ class EventListenerCacheBuilder extends AbstractCacheBuilder {
 			ORDER BY	niceValue ASC, listenerClassName ASC";
 		$statement = WCF::getDB()->prepareStatement($sql);
 		$statement->execute();
-		while ($eventListener = $statement->fetchObject('wcf\data\event\listener\EventListener')) {
+		while ($eventListener = $statement->fetchObject(EventListener::class)) {
 			$eventNames = $eventListener->getEventNames();
 			
 			if (!$eventListener->inherit) {
diff --git a/wcfsetup/install/files/lib/system/cache/builder/OptionCacheBuilder.class.php b/wcfsetup/install/files/lib/system/cache/builder/OptionCacheBuilder.class.php
index afb0a32bcb..920dd82dc5 100644
--- a/wcfsetup/install/files/lib/system/cache/builder/OptionCacheBuilder.class.php
+++ b/wcfsetup/install/files/lib/system/cache/builder/OptionCacheBuilder.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\system\cache\builder;
 use wcf\data\option\category\OptionCategory;
+use wcf\data\option\Option;
 use wcf\system\WCF;
 
 /**
@@ -18,7 +19,7 @@ class OptionCacheBuilder extends AbstractCacheBuilder {
 	 * option class name
 	 * @var	string
 	 */
-	protected $optionClassName = 'wcf\data\option\Option';
+	protected $optionClassName = Option::class;
 	
 	/**
 	 * database table name
diff --git a/wcfsetup/install/files/lib/system/cache/builder/SmileyCacheBuilder.class.php b/wcfsetup/install/files/lib/system/cache/builder/SmileyCacheBuilder.class.php
index da7358ba97..56b1d33a8f 100644
--- a/wcfsetup/install/files/lib/system/cache/builder/SmileyCacheBuilder.class.php
+++ b/wcfsetup/install/files/lib/system/cache/builder/SmileyCacheBuilder.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\cache\builder;
+use wcf\data\smiley\Smiley;
 use wcf\system\WCF;
 
 /**
@@ -25,7 +26,7 @@ class SmileyCacheBuilder extends AbstractCacheBuilder {
 			ORDER BY	showOrder";
 		$statement = WCF::getDB()->prepareStatement($sql);
 		$statement->execute();
-		while ($object = $statement->fetchObject('wcf\data\smiley\Smiley')) {
+		while ($object = $statement->fetchObject(Smiley::class)) {
 			$object->smileyCodes = $object->getAliases();
 			$object->smileyCodes[] = $object->smileyCode;
 			
diff --git a/wcfsetup/install/files/lib/system/cache/builder/UserGroupOptionCacheBuilder.class.php b/wcfsetup/install/files/lib/system/cache/builder/UserGroupOptionCacheBuilder.class.php
index 01ce3059ab..95741fbb08 100644
--- a/wcfsetup/install/files/lib/system/cache/builder/UserGroupOptionCacheBuilder.class.php
+++ b/wcfsetup/install/files/lib/system/cache/builder/UserGroupOptionCacheBuilder.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\cache\builder;
+use wcf\data\user\group\option\UserGroupOption;
 
 /**
  * Caches user group options and categories
@@ -15,7 +16,7 @@ class UserGroupOptionCacheBuilder extends OptionCacheBuilder {
 	/**
 	 * @inheritDoc
 	 */
-	protected $optionClassName = 'wcf\data\user\group\option\UserGroupOption';
+	protected $optionClassName = UserGroupOption::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/cache/builder/UserGroupPermissionCacheBuilder.class.php b/wcfsetup/install/files/lib/system/cache/builder/UserGroupPermissionCacheBuilder.class.php
index 96cf030616..313d972b63 100644
--- a/wcfsetup/install/files/lib/system/cache/builder/UserGroupPermissionCacheBuilder.class.php
+++ b/wcfsetup/install/files/lib/system/cache/builder/UserGroupPermissionCacheBuilder.class.php
@@ -97,8 +97,8 @@ class UserGroupPermissionCacheBuilder extends AbstractCacheBuilder {
 			if (!class_exists($className)) {
 				throw new SystemException("unable to find class '".$className."'");
 			}
-			if (!is_subclass_of($className, 'wcf\system\option\user\group\IUserGroupOptionType')) {
-				throw new SystemException("'".$className."' does not implement 'wcf\system\option\user\group\IUserGroupOptionType'");
+			if (!is_subclass_of($className, IUserGroupOptionType::class)) {
+				throw new SystemException("'".$className."' does not implement '".IUserGroupOptionType::class."'");
 			}
 			
 			// create instance
diff --git a/wcfsetup/install/files/lib/system/cache/builder/UserMenuCacheBuilder.class.php b/wcfsetup/install/files/lib/system/cache/builder/UserMenuCacheBuilder.class.php
index 6149f86811..e236b4422c 100644
--- a/wcfsetup/install/files/lib/system/cache/builder/UserMenuCacheBuilder.class.php
+++ b/wcfsetup/install/files/lib/system/cache/builder/UserMenuCacheBuilder.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\system\cache\builder;
 use wcf\data\user\menu\item\UserMenuItem;
+use wcf\form\SettingsForm;
 use wcf\system\WCF;
 
 /**
@@ -38,7 +39,7 @@ class UserMenuCacheBuilder extends AbstractCacheBuilder {
 				'packageID' => $row['packageID'],
 				'menuItem' => 'wcf.user.option.category.'.$row['categoryName'],
 				'parentMenuItem' => 'wcf.user.menu.settings',
-				'menuItemController' => 'wcf\form\SettingsForm',
+				'menuItemController' => SettingsForm::class,
 				'menuItemLink' => ($categoryShortName != 'general' ? 'category='.$categoryShortName : ''),
 				'permissions' => $row['permissions'],
 				'options' => $row['options']
diff --git a/wcfsetup/install/files/lib/system/cache/builder/UserOptionCacheBuilder.class.php b/wcfsetup/install/files/lib/system/cache/builder/UserOptionCacheBuilder.class.php
index 25f2ab0fa8..6ca556a367 100644
--- a/wcfsetup/install/files/lib/system/cache/builder/UserOptionCacheBuilder.class.php
+++ b/wcfsetup/install/files/lib/system/cache/builder/UserOptionCacheBuilder.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\cache\builder;
+use wcf\data\user\option\UserOption;
 
 /**
  * Caches user options and categories
@@ -15,7 +16,7 @@ class UserOptionCacheBuilder extends OptionCacheBuilder {
 	/**
 	 * @inheritDoc
 	 */
-	protected $optionClassName = 'wcf\data\user\option\UserOption';
+	protected $optionClassName = UserOption::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/cache/builder/UserStatsCacheBuilder.class.php b/wcfsetup/install/files/lib/system/cache/builder/UserStatsCacheBuilder.class.php
index 83084f35df..5ba5235390 100644
--- a/wcfsetup/install/files/lib/system/cache/builder/UserStatsCacheBuilder.class.php
+++ b/wcfsetup/install/files/lib/system/cache/builder/UserStatsCacheBuilder.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\cache\builder;
+use wcf\data\user\User;
 use wcf\system\WCF;
 
 /**
@@ -37,7 +38,7 @@ class UserStatsCacheBuilder extends AbstractCacheBuilder {
 			ORDER BY	userID DESC";
 		$statement = WCF::getDB()->prepareStatement($sql, 1);
 		$statement->execute();
-		$data['newestMember'] = $statement->fetchObject('wcf\data\user\User');
+		$data['newestMember'] = $statement->fetchObject(User::class);
 		
 		return $data;
 	}
diff --git a/wcfsetup/install/files/lib/system/cli/command/WorkerCLICommand.class.php b/wcfsetup/install/files/lib/system/cli/command/WorkerCLICommand.class.php
index 4ca2181a0c..42ca44c8d7 100644
--- a/wcfsetup/install/files/lib/system/cli/command/WorkerCLICommand.class.php
+++ b/wcfsetup/install/files/lib/system/cli/command/WorkerCLICommand.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\system\cli\command;
 use phpline\internal\Log;
+use wcf\system\worker\IWorker;
 use wcf\system\CLIWCF;
 use wcf\system\Regex;
 use wcf\util\CLIUtil;
@@ -77,7 +78,7 @@ class WorkerCLICommand implements IArgumentedCLICommand {
 			if (!$reflection->isInstantiable()) {
 				$invalid = true;
 			}
-			else if (!is_subclass_of($class, 'wcf\system\worker\IWorker')) {
+			else if (!is_subclass_of($class, IWorker::class)) {
 				$invalid = true;
 			}
 		}
@@ -155,7 +156,7 @@ class WorkerCLICommand implements IArgumentedCLICommand {
 			$reflection = new \ReflectionClass($class);
 			if (!$reflection->isInstantiable()) continue;
 			
-			if (!is_subclass_of($class, 'wcf\system\worker\IWorker')) {
+			if (!is_subclass_of($class, IWorker::class)) {
 				Log::info('Invalid worker file: ', $worker);
 				continue;
 			}
diff --git a/wcfsetup/install/files/lib/system/clipboard/ClipboardHandler.class.php b/wcfsetup/install/files/lib/system/clipboard/ClipboardHandler.class.php
index 28c6f80c64..c37b9b4fb4 100644
--- a/wcfsetup/install/files/lib/system/clipboard/ClipboardHandler.class.php
+++ b/wcfsetup/install/files/lib/system/clipboard/ClipboardHandler.class.php
@@ -4,6 +4,7 @@ use wcf\data\object\type\ObjectTypeCache;
 use wcf\data\DatabaseObject;
 use wcf\system\cache\builder\ClipboardActionCacheBuilder;
 use wcf\system\cache\builder\ClipboardPageCacheBuilder;
+use wcf\system\clipboard\action\IClipboardAction;
 use wcf\system\database\util\PreparedStatementConditionBuilder;
 use wcf\system\exception\SystemException;
 use wcf\system\SingletonFactory;
@@ -323,8 +324,8 @@ class ClipboardHandler extends SingletonFactory {
 			$actionClassName = $actionObject->actionClassName;
 			if (!isset($actions[$actionClassName])) {
 				// validate class
-				if (!is_subclass_of($actionClassName, 'wcf\system\clipboard\action\IClipboardAction')) {
-					throw new SystemException("'".$actionClassName."' does not implement 'wcf\system\clipboard\action\IClipboardAction'");
+				if (!is_subclass_of($actionClassName, IClipboardAction::class)) {
+					throw new SystemException("'".$actionClassName."' does not implement '".IClipboardAction::class."'");
 				}
 				
 				$actions[$actionClassName] = [
diff --git a/wcfsetup/install/files/lib/system/clipboard/action/TagClipboardAction.class.php b/wcfsetup/install/files/lib/system/clipboard/action/TagClipboardAction.class.php
index 2490a97ff7..4be20cbe21 100644
--- a/wcfsetup/install/files/lib/system/clipboard/action/TagClipboardAction.class.php
+++ b/wcfsetup/install/files/lib/system/clipboard/action/TagClipboardAction.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\system\clipboard\action;
 use wcf\data\clipboard\action\ClipboardAction;
+use wcf\data\tag\TagAction;
 use wcf\system\WCF;
 
 /**
@@ -57,7 +58,7 @@ class TagClipboardAction extends AbstractClipboardAction {
 	 * @inheritDoc
 	 */
 	public function getClassName() {
-		return 'wcf\data\tag\TagAction';
+		return TagAction::class;
 	}
 	
 	/**
diff --git a/wcfsetup/install/files/lib/system/clipboard/action/UserClipboardAction.class.php b/wcfsetup/install/files/lib/system/clipboard/action/UserClipboardAction.class.php
index 6d6fe4dc88..6b69f7c995 100644
--- a/wcfsetup/install/files/lib/system/clipboard/action/UserClipboardAction.class.php
+++ b/wcfsetup/install/files/lib/system/clipboard/action/UserClipboardAction.class.php
@@ -2,6 +2,7 @@
 namespace wcf\system\clipboard\action;
 use wcf\data\clipboard\action\ClipboardAction;
 use wcf\data\user\group\UserGroup;
+use wcf\data\user\UserAction;
 use wcf\system\database\util\PreparedStatementConditionBuilder;
 use wcf\system\request\LinkHandler;
 use wcf\system\WCF;
@@ -75,7 +76,7 @@ class UserClipboardAction extends AbstractClipboardAction {
 	 * @inheritDoc
 	 */
 	public function getClassName() {
-		return 'wcf\data\user\UserAction';
+		return UserAction::class;
 	}
 	
 	/**
diff --git a/wcfsetup/install/files/lib/system/clipboard/action/UserContentClipboardAction.class.php b/wcfsetup/install/files/lib/system/clipboard/action/UserContentClipboardAction.class.php
index 0589aec39a..65a21d7737 100644
--- a/wcfsetup/install/files/lib/system/clipboard/action/UserContentClipboardAction.class.php
+++ b/wcfsetup/install/files/lib/system/clipboard/action/UserContentClipboardAction.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\system\clipboard\action;
 use wcf\data\clipboard\action\ClipboardAction;
+use wcf\data\user\UserContentAction;
 use wcf\system\request\LinkHandler;
 use wcf\system\WCF;
 
@@ -44,7 +45,7 @@ class UserContentClipboardAction extends AbstractClipboardAction {
 	 * @inheritDoc
 	 */
 	public function getClassName() {
-		return 'wcf\data\user\UserContentAction';
+		return UserContentAction::class;
 	}
 	
 	/**
diff --git a/wcfsetup/install/files/lib/system/cronjob/CronjobScheduler.class.php b/wcfsetup/install/files/lib/system/cronjob/CronjobScheduler.class.php
index 6ae71b538d..950c1834df 100644
--- a/wcfsetup/install/files/lib/system/cronjob/CronjobScheduler.class.php
+++ b/wcfsetup/install/files/lib/system/cronjob/CronjobScheduler.class.php
@@ -173,8 +173,8 @@ class CronjobScheduler extends SingletonFactory {
 		}
 		
 		// verify class signature
-		if (!(is_subclass_of($className, 'wcf\system\cronjob\ICronjob'))) {
-			throw new SystemException("'".$className."' does not implement 'wcf\system\cronjob\ICronjob'");
+		if (!(is_subclass_of($className, ICronjob::class))) {
+			throw new SystemException("'".$className."' does not implement '".ICronjob::class."'");
 		}
 		
 		// execute cronjob
diff --git a/wcfsetup/install/files/lib/system/database/Database.class.php b/wcfsetup/install/files/lib/system/database/Database.class.php
index 5d462a91dc..6ce0630fa7 100644
--- a/wcfsetup/install/files/lib/system/database/Database.class.php
+++ b/wcfsetup/install/files/lib/system/database/Database.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\system\database;
 use wcf\system\benchmark\Benchmark;
+use wcf\system\database\editor\DatabaseEditor;
 use wcf\system\database\exception\DatabaseException as GenericDatabaseException;
 use wcf\system\database\exception\DatabaseQueryException;
 use wcf\system\database\exception\DatabaseTransactionException;
@@ -22,13 +23,13 @@ abstract class Database {
 	 * name of the class used for prepared statements
 	 * @var	string
 	 */
-	protected $preparedStatementClassName = 'wcf\system\database\statement\PreparedStatement';
+	protected $preparedStatementClassName = PreparedStatement::class;
 	
 	/**
 	 * name of the database editor class
 	 * @var	string
 	 */
-	protected $editorClassName = 'wcf\system\database\editor\DatabaseEditor';
+	protected $editorClassName = DatabaseEditor::class;
 	
 	/**
 	 * sql server hostname
diff --git a/wcfsetup/install/files/lib/system/database/MySQLDatabase.class.php b/wcfsetup/install/files/lib/system/database/MySQLDatabase.class.php
index 59ba7ef8d3..a02b761c33 100644
--- a/wcfsetup/install/files/lib/system/database/MySQLDatabase.class.php
+++ b/wcfsetup/install/files/lib/system/database/MySQLDatabase.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\database;
+use wcf\system\database\editor\MySQLDatabaseEditor;
 use wcf\system\database\exception\DatabaseException as GenericDatabaseException;
 
 /**
@@ -16,7 +17,7 @@ class MySQLDatabase extends Database {
 	/**
 	 * @inheritDoc
 	 */
-	protected $editorClassName = 'wcf\system\database\editor\MySQLDatabaseEditor';
+	protected $editorClassName = MySQLDatabaseEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/database/PostgreSQLDatabase.class.php b/wcfsetup/install/files/lib/system/database/PostgreSQLDatabase.class.php
index 41ab00ee8e..04f66c7361 100644
--- a/wcfsetup/install/files/lib/system/database/PostgreSQLDatabase.class.php
+++ b/wcfsetup/install/files/lib/system/database/PostgreSQLDatabase.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\database;
+use wcf\system\database\editor\PostgreSQLDatabaseEditor;
 use wcf\system\database\exception\DatabaseException as GenericDatabaseException;
 use wcf\util\StringStack;
 
@@ -17,7 +18,7 @@ class PostgreSQLDatabase extends Database {
 	/**
 	 * @inheritDoc
 	 */
-	protected $editorClassName = 'wcf\system\database\editor\PostgreSQLDatabaseEditor';
+	protected $editorClassName = PostgreSQLDatabaseEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/event/EventHandler.class.php b/wcfsetup/install/files/lib/system/event/EventHandler.class.php
index cfd68ad34f..a3db6b5893 100644
--- a/wcfsetup/install/files/lib/system/event/EventHandler.class.php
+++ b/wcfsetup/install/files/lib/system/event/EventHandler.class.php
@@ -113,10 +113,10 @@ class EventHandler extends SingletonFactory {
 									if (!class_exists($eventListener->listenerClassName)) {
 										throw new SystemException("Unable to find class '".$eventListener->listenerClassName."'");
 									}
-									if (!is_subclass_of($eventListener->listenerClassName, 'wcf\system\event\listener\IParameterizedEventListener')) {
+									if (!is_subclass_of($eventListener->listenerClassName, IParameterizedEventListener::class)) {
 										// legacy event listeners
-										if (!is_subclass_of($eventListener->listenerClassName, 'wcf\system\event\IEventListener')) {
-											throw new SystemException("'".$eventListener->listenerClassName."' does not implement 'wcf\system\event\listener\IParameterizedEventListener'");
+										if (!is_subclass_of($eventListener->listenerClassName, IEventListener::class)) {
+											throw new SystemException("'".$eventListener->listenerClassName."' does not implement '".IParameterizedEventListener::class."'");
 										}
 									}
 									
@@ -200,10 +200,10 @@ class EventHandler extends SingletonFactory {
 						if (!class_exists($eventListener->listenerClassName)) {
 							throw new SystemException("Unable to find class '".$eventListener->listenerClassName."'");
 						}
-						if (!is_subclass_of($eventListener->listenerClassName, 'wcf\system\event\listener\IParameterizedEventListener')) {
+						if (!is_subclass_of($eventListener->listenerClassName, IParameterizedEventListener::class)) {
 							// legacy event listeners
-							if (!is_subclass_of($eventListener->listenerClassName, 'wcf\system\event\IEventListener')) {
-								throw new SystemException("'".$eventListener->listenerClassName."' does not implement 'wcf\system\event\listener\IParameterizedEventListener'");
+							if (!is_subclass_of($eventListener->listenerClassName, IEventListener::class)) {
+								throw new SystemException("'".$eventListener->listenerClassName."' does not implement '".IParameterizedEventListener::class."'");
 							}
 						}
 						
diff --git a/wcfsetup/install/files/lib/system/form/element/MultipleSelectionFormElement.class.php b/wcfsetup/install/files/lib/system/form/element/MultipleSelectionFormElement.class.php
index a08c471567..1d3f75ecc9 100644
--- a/wcfsetup/install/files/lib/system/form/element/MultipleSelectionFormElement.class.php
+++ b/wcfsetup/install/files/lib/system/form/element/MultipleSelectionFormElement.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\form\element;
+use wcf\util\StringUtil;
 
 /**
  * Provides a checkbox form element.
@@ -26,7 +27,7 @@ class MultipleSelectionFormElement extends AbstractNamedFormElement {
 			parent::setValue($value);
 		}
 		else {
-			$this->value = array_map(['wcf\util\StringUtil', 'trim'], $value);
+			$this->value = array_map([StringUtil::class, 'trim'], $value);
 		}
 	}
 	
diff --git a/wcfsetup/install/files/lib/system/image/ImageHandler.class.php b/wcfsetup/install/files/lib/system/image/ImageHandler.class.php
index 92fcea92fa..186be4cca4 100644
--- a/wcfsetup/install/files/lib/system/image/ImageHandler.class.php
+++ b/wcfsetup/install/files/lib/system/image/ImageHandler.class.php
@@ -1,7 +1,9 @@
 <?php
 namespace wcf\system\image;
 use wcf\system\exception\SystemException;
+use wcf\system\image\adapter\GDImageAdapter;
 use wcf\system\image\adapter\ImageAdapter;
+use wcf\system\image\adapter\ImagickImageAdapter;
 use wcf\system\SingletonFactory;
 
 /**
@@ -20,8 +22,8 @@ class ImageHandler extends SingletonFactory {
 	 * @var	string[]
 	 */
 	protected $imageAdapters = [
-		'gd' => 'wcf\system\image\adapter\GDImageAdapter',
-		'imagick' => 'wcf\system\image\adapter\ImagickImageAdapter'
+		'gd' => GDImageAdapter::class,
+		'imagick' => ImagickImageAdapter::class
 	];
 	
 	/**
diff --git a/wcfsetup/install/files/lib/system/importer/AbstractAttachmentImporter.class.php b/wcfsetup/install/files/lib/system/importer/AbstractAttachmentImporter.class.php
index e6adc260e2..61701ee535 100644
--- a/wcfsetup/install/files/lib/system/importer/AbstractAttachmentImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/AbstractAttachmentImporter.class.php
@@ -18,7 +18,7 @@ class AbstractAttachmentImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\attachment\Attachment';
+	protected $className = Attachment::class;
 	
 	/**
 	 * object type id for attachments
diff --git a/wcfsetup/install/files/lib/system/importer/AbstractCategoryImporter.class.php b/wcfsetup/install/files/lib/system/importer/AbstractCategoryImporter.class.php
index eaca3b785d..b748d63132 100644
--- a/wcfsetup/install/files/lib/system/importer/AbstractCategoryImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/AbstractCategoryImporter.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\importer;
+use wcf\data\category\Category;
 use wcf\data\category\CategoryEditor;
 
 /**
@@ -16,7 +17,7 @@ class AbstractCategoryImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\category\Category';
+	protected $className = Category::class;
 	
 	/**
 	 * object type id for categories
diff --git a/wcfsetup/install/files/lib/system/importer/AbstractCommentImporter.class.php b/wcfsetup/install/files/lib/system/importer/AbstractCommentImporter.class.php
index 4cadad506a..d67b32b203 100644
--- a/wcfsetup/install/files/lib/system/importer/AbstractCommentImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/AbstractCommentImporter.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\importer;
+use wcf\data\comment\Comment;
 use wcf\data\comment\CommentEditor;
 
 /**
@@ -16,7 +17,7 @@ class AbstractCommentImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\comment\Comment';
+	protected $className = Comment::class;
 	
 	/**
 	 * object type id for comments
diff --git a/wcfsetup/install/files/lib/system/importer/AbstractCommentResponseImporter.class.php b/wcfsetup/install/files/lib/system/importer/AbstractCommentResponseImporter.class.php
index 7f11298bc2..a04ae63f1d 100644
--- a/wcfsetup/install/files/lib/system/importer/AbstractCommentResponseImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/AbstractCommentResponseImporter.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\importer;
+use wcf\data\comment\response\CommentResponse;
 use wcf\data\comment\response\CommentResponseEditor;
 use wcf\system\WCF;
 
@@ -17,7 +18,7 @@ class AbstractCommentResponseImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\comment\response\CommentResponse';
+	protected $className = CommentResponse::class;
 	
 	/**
 	 * object type name
diff --git a/wcfsetup/install/files/lib/system/importer/AbstractLikeImporter.class.php b/wcfsetup/install/files/lib/system/importer/AbstractLikeImporter.class.php
index f4d4df3554..77c36c1ebd 100644
--- a/wcfsetup/install/files/lib/system/importer/AbstractLikeImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/AbstractLikeImporter.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\importer;
+use wcf\data\like\Like;
 use wcf\system\WCF;
 
 /**
@@ -16,7 +17,7 @@ class AbstractLikeImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\like\Like';
+	protected $className = Like::class;
 	
 	/**
 	 * object type id for likes
diff --git a/wcfsetup/install/files/lib/system/importer/AbstractPollImporter.class.php b/wcfsetup/install/files/lib/system/importer/AbstractPollImporter.class.php
index 1802eae036..3e3b35b7b8 100644
--- a/wcfsetup/install/files/lib/system/importer/AbstractPollImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/AbstractPollImporter.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\importer;
+use wcf\data\poll\Poll;
 use wcf\data\poll\PollEditor;
 
 /**
@@ -16,7 +17,7 @@ class AbstractPollImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\poll\Poll';
+	protected $className = Poll::class;
 	
 	/**
 	 * object type id for poll
diff --git a/wcfsetup/install/files/lib/system/importer/AbstractPollOptionImporter.class.php b/wcfsetup/install/files/lib/system/importer/AbstractPollOptionImporter.class.php
index e51f70daed..2ff536fd8c 100644
--- a/wcfsetup/install/files/lib/system/importer/AbstractPollOptionImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/AbstractPollOptionImporter.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\importer;
+use wcf\data\poll\option\PollOption;
 use wcf\data\poll\option\PollOptionEditor;
 
 /**
@@ -16,7 +17,7 @@ class AbstractPollOptionImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\poll\option\PollOption';
+	protected $className = PollOption::class;
 	
 	/**
 	 * option object type name
diff --git a/wcfsetup/install/files/lib/system/importer/AbstractWatchedObjectImporter.class.php b/wcfsetup/install/files/lib/system/importer/AbstractWatchedObjectImporter.class.php
index 9fe76efac6..db9b388492 100644
--- a/wcfsetup/install/files/lib/system/importer/AbstractWatchedObjectImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/AbstractWatchedObjectImporter.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\importer;
+use wcf\data\user\object\watch\UserObjectWatch;
 use wcf\data\user\object\watch\UserObjectWatchEditor;
 use wcf\system\database\DatabaseException;
 
@@ -17,7 +18,7 @@ class AbstractWatchedObjectImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\user\object\watch';
+	protected $className = UserObjectWatch::class;
 	
 	/**
 	 * object type id for watched objects
diff --git a/wcfsetup/install/files/lib/system/importer/LabelGroupImporter.class.php b/wcfsetup/install/files/lib/system/importer/LabelGroupImporter.class.php
index ba371f863e..7fb7326548 100644
--- a/wcfsetup/install/files/lib/system/importer/LabelGroupImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/LabelGroupImporter.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\importer;
+use wcf\data\label\group\LabelGroup;
 use wcf\data\label\group\LabelGroupEditor;
 use wcf\system\WCF;
 
@@ -17,7 +18,7 @@ class LabelGroupImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\label\group\LabelGroup';
+	protected $className = LabelGroup::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/importer/LabelImporter.class.php b/wcfsetup/install/files/lib/system/importer/LabelImporter.class.php
index 43e995fc4a..755a8c5b33 100644
--- a/wcfsetup/install/files/lib/system/importer/LabelImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/LabelImporter.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\importer;
+use wcf\data\label\Label;
 use wcf\data\label\LabelEditor;
 
 /**
@@ -16,7 +17,7 @@ class LabelImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\label\Label';
+	protected $className = Label::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/importer/SmileyImporter.class.php b/wcfsetup/install/files/lib/system/importer/SmileyImporter.class.php
index 9315531433..6620624bd0 100644
--- a/wcfsetup/install/files/lib/system/importer/SmileyImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/SmileyImporter.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\importer;
+use wcf\data\smiley\Smiley;
 use wcf\data\smiley\SmileyEditor;
 use wcf\system\WCF;
 use wcf\util\StringUtil;
@@ -18,11 +19,10 @@ class SmileyImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\smiley\Smiley';
+	protected $className = Smiley::class;
 	
 	/**
 	 * known smiley codes
-	 * 
 	 * @var	string[]
 	 */
 	public $knownCodes = [];
diff --git a/wcfsetup/install/files/lib/system/importer/UserAvatarImporter.class.php b/wcfsetup/install/files/lib/system/importer/UserAvatarImporter.class.php
index 129adb65f3..89f6bb99dd 100644
--- a/wcfsetup/install/files/lib/system/importer/UserAvatarImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/UserAvatarImporter.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\importer;
+use wcf\data\user\avatar\UserAvatar;
 use wcf\data\user\avatar\UserAvatarAction;
 use wcf\data\user\avatar\UserAvatarEditor;
 use wcf\system\exception\SystemException;
@@ -20,7 +21,7 @@ class UserAvatarImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\user\avatar\UserAvatar';
+	protected $className = UserAvatar::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/importer/UserFollowerImporter.class.php b/wcfsetup/install/files/lib/system/importer/UserFollowerImporter.class.php
index a8f3a1f8d9..9da44442e6 100644
--- a/wcfsetup/install/files/lib/system/importer/UserFollowerImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/UserFollowerImporter.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\importer;
+use wcf\data\user\follow\UserFollow;
 use wcf\system\WCF;
 
 /**
@@ -16,7 +17,7 @@ class UserFollowerImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\user\follow\UserFollow';
+	protected $className = UserFollow::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/importer/UserGroupImporter.class.php b/wcfsetup/install/files/lib/system/importer/UserGroupImporter.class.php
index fd8658b404..495f2ffbea 100644
--- a/wcfsetup/install/files/lib/system/importer/UserGroupImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/UserGroupImporter.class.php
@@ -17,7 +17,7 @@ class UserGroupImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\user\group\UserGroup';
+	protected $className = UserGroup::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/importer/UserImporter.class.php b/wcfsetup/install/files/lib/system/importer/UserImporter.class.php
index bf1178e09e..576152af1f 100644
--- a/wcfsetup/install/files/lib/system/importer/UserImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/UserImporter.class.php
@@ -22,7 +22,7 @@ class UserImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\user\User';
+	protected $className = User::class;
 	
 	/**
 	 * ids of default notification events
diff --git a/wcfsetup/install/files/lib/system/importer/UserOptionImporter.class.php b/wcfsetup/install/files/lib/system/importer/UserOptionImporter.class.php
index 956e8a46ce..37e71be609 100644
--- a/wcfsetup/install/files/lib/system/importer/UserOptionImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/UserOptionImporter.class.php
@@ -2,6 +2,7 @@
 namespace wcf\system\importer;
 use wcf\data\user\option\category\UserOptionCategoryEditor;
 use wcf\data\user\option\category\UserOptionCategoryList;
+use wcf\data\user\option\UserOption;
 use wcf\data\user\option\UserOptionAction;
 use wcf\data\user\option\UserOptionEditor;
 use wcf\system\language\LanguageFactory;
@@ -22,7 +23,7 @@ class UserOptionImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\user\option\UserOption';
+	protected $className = UserOption::class;
 	
 	/**
 	 * language category id
diff --git a/wcfsetup/install/files/lib/system/importer/UserRankImporter.class.php b/wcfsetup/install/files/lib/system/importer/UserRankImporter.class.php
index 426ce9af0a..bff159bd87 100644
--- a/wcfsetup/install/files/lib/system/importer/UserRankImporter.class.php
+++ b/wcfsetup/install/files/lib/system/importer/UserRankImporter.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\system\importer;
 use wcf\data\user\group\UserGroup;
+use wcf\data\user\rank\UserRank;
 use wcf\data\user\rank\UserRankEditor;
 
 /**
@@ -17,7 +18,7 @@ class UserRankImporter extends AbstractImporter {
 	/**
 	 * @inheritDoc
 	 */
-	protected $className = 'wcf\data\user\rank\UserRank';
+	protected $className = UserRank::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/label/LabelHandler.class.php b/wcfsetup/install/files/lib/system/label/LabelHandler.class.php
index 50f950d0ca..58261ce970 100644
--- a/wcfsetup/install/files/lib/system/label/LabelHandler.class.php
+++ b/wcfsetup/install/files/lib/system/label/LabelHandler.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\label;
+use wcf\data\label\group\LabelGroup;
 use wcf\data\label\group\ViewableLabelGroup;
 use wcf\data\object\type\ObjectTypeCache;
 use wcf\system\cache\builder\LabelCacheBuilder;
@@ -305,7 +306,7 @@ class LabelHandler extends SingletonFactory {
 			$data[$groupID] = $this->labelGroups['groups'][$groupID];
 		}
 		
-		uasort($data, ['\wcf\data\label\group\LabelGroup', 'sortLabelGroups']);
+		uasort($data, [LabelGroup::class, 'sortLabelGroups']);
 		
 		return $data;
 	}
diff --git a/wcfsetup/install/files/lib/system/label/object/AbstractLabelObjectHandler.class.php b/wcfsetup/install/files/lib/system/label/object/AbstractLabelObjectHandler.class.php
index 42c53308b2..2427575760 100644
--- a/wcfsetup/install/files/lib/system/label/object/AbstractLabelObjectHandler.class.php
+++ b/wcfsetup/install/files/lib/system/label/object/AbstractLabelObjectHandler.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\label\object;
+use wcf\data\label\group\LabelGroup;
 use wcf\data\label\group\ViewableLabelGroup;
 use wcf\system\exception\SystemException;
 use wcf\system\label\LabelHandler;
@@ -65,7 +66,7 @@ abstract class AbstractLabelObjectHandler extends SingletonFactory implements IL
 			$data[$groupID] = $this->labelGroups[$groupID];
 		}
 		
-		uasort($data, ['\wcf\data\label\group\LabelGroup', 'sortLabelGroups']);
+		uasort($data, [LabelGroup::class, 'sortLabelGroups']);
 		
 		return $data;
 	}
diff --git a/wcfsetup/install/files/lib/system/message/QuickReplyManager.class.php b/wcfsetup/install/files/lib/system/message/QuickReplyManager.class.php
index b775bbc0da..4977567595 100644
--- a/wcfsetup/install/files/lib/system/message/QuickReplyManager.class.php
+++ b/wcfsetup/install/files/lib/system/message/QuickReplyManager.class.php
@@ -4,6 +4,7 @@ use wcf\data\DatabaseObjectDecorator;
 use wcf\data\IAttachmentMessageQuickReplyAction;
 use wcf\data\IMessage;
 use wcf\data\IMessageQuickReplyAction;
+use wcf\data\IVisitableObjectAction;
 use wcf\system\bbcode\PreParser;
 use wcf\system\event\EventHandler;
 use wcf\system\exception\SystemException;
@@ -135,8 +136,8 @@ class QuickReplyManager extends SingletonFactory {
 		
 		$this->container = new $containerClassName($parameters['objectID']);
 		if (!empty($containerDecoratorClassName)) {
-			if (!is_subclass_of($containerDecoratorClassName, 'wcf\data\DatabaseObjectDecorator')) {
-				throw new SystemException("'".$containerDecoratorClassName."' does not extend 'wcf\data\DatabaseObjectDecorator'");
+			if (!is_subclass_of($containerDecoratorClassName, DatabaseObjectDecorator::class)) {
+				throw new SystemException("'".$containerDecoratorClassName."' does not extend '".DatabaseObjectDecorator::class."'");
 			}
 			
 			$this->container = new $containerDecoratorClassName($this->container);
@@ -234,7 +235,7 @@ class QuickReplyManager extends SingletonFactory {
 			}
 			
 			// update visit time (messages shouldn't occur as new upon next visit)
-			if (is_subclass_of($containerActionClassName, 'wcf\data\IVisitableObjectAction')) {
+			if (is_subclass_of($containerActionClassName, IVisitableObjectAction::class)) {
 				$containerAction = new $containerActionClassName([($this->container instanceof DatabaseObjectDecorator ? $this->container->getDecoratedObject() : $this->container)], 'markAsRead');
 				$containerAction->executeAction();
 			}
diff --git a/wcfsetup/install/files/lib/system/moderation/queue/AbstractModerationQueueHandler.class.php b/wcfsetup/install/files/lib/system/moderation/queue/AbstractModerationQueueHandler.class.php
index ebeee96193..a664f54bb4 100644
--- a/wcfsetup/install/files/lib/system/moderation/queue/AbstractModerationQueueHandler.class.php
+++ b/wcfsetup/install/files/lib/system/moderation/queue/AbstractModerationQueueHandler.class.php
@@ -4,6 +4,7 @@ use wcf\data\moderation\queue\ModerationQueue;
 use wcf\data\moderation\queue\ModerationQueueAction;
 use wcf\data\user\User;
 use wcf\data\user\UserProfile;
+use wcf\data\DatabaseObject;
 use wcf\system\database\util\PreparedStatementConditionBuilder;
 use wcf\system\exception\SystemException;
 use wcf\system\moderation\queue\activation\IModerationQueueActivationHandler;
@@ -49,7 +50,7 @@ abstract class AbstractModerationQueueHandler implements IModerationQueueHandler
 	 * @inheritDoc
 	 */
 	public function identifyOrphans(array $queues) {
-		if (empty($this->className) || !class_exists($this->className) || !is_subclass_of($this->className, 'wcf\data\DatabaseObject')) {
+		if (empty($this->className) || !class_exists($this->className) || !is_subclass_of($this->className, DatabaseObject::class)) {
 			throw new SystemException("DatabaseObject class name '" . $this->className . "' is missing or invalid");
 		}
 		
diff --git a/wcfsetup/install/files/lib/system/option/AbstractCategoryMultiSelectOptionType.class.php b/wcfsetup/install/files/lib/system/option/AbstractCategoryMultiSelectOptionType.class.php
index ec936b496a..12358c0138 100644
--- a/wcfsetup/install/files/lib/system/option/AbstractCategoryMultiSelectOptionType.class.php
+++ b/wcfsetup/install/files/lib/system/option/AbstractCategoryMultiSelectOptionType.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\option;
+use wcf\data\category\CategoryNodeTree;
 use wcf\data\option\Option;
 use wcf\system\category\CategoryHandler;
 use wcf\system\exception\UserInputException;
@@ -27,7 +28,7 @@ abstract class AbstractCategoryMultiSelectOptionType extends AbstractOptionType
 	 * node tree class
 	 * @var	string
 	 */
-	public $nodeTreeClassname = 'wcf\data\category\CategoryNodeTree';
+	public $nodeTreeClassname = CategoryNodeTree::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/option/FileOptionType.class.php b/wcfsetup/install/files/lib/system/option/FileOptionType.class.php
index 876d198120..c77ae3cd7b 100644
--- a/wcfsetup/install/files/lib/system/option/FileOptionType.class.php
+++ b/wcfsetup/install/files/lib/system/option/FileOptionType.class.php
@@ -110,7 +110,7 @@ class FileOptionType extends AbstractOptionType {
 		if ($option->filevalidation) {
 			$fileValidation = new $option->filevalidation();
 			if (!($fileValidation instanceof IUploadFileValidationStrategy)) {
-				throw new SystemException("The file validation class needs to implement 'wcf\system\upload\IUploadFileValidationStrategy'");
+				throw new SystemException("The file validation class needs to implement '".IUploadFileValidationStrategy::class."'");
 			}
 			
 			if (!$this->uploadHandlers[$option->optionName]->validateFiles($fileValidation)) {
diff --git a/wcfsetup/install/files/lib/system/option/OptionHandler.class.php b/wcfsetup/install/files/lib/system/option/OptionHandler.class.php
index e9b7f736b1..16a98ffb31 100644
--- a/wcfsetup/install/files/lib/system/option/OptionHandler.class.php
+++ b/wcfsetup/install/files/lib/system/option/OptionHandler.class.php
@@ -3,6 +3,7 @@ namespace wcf\system\option;
 use wcf\data\option\category\OptionCategory;
 use wcf\data\option\Option;
 use wcf\system\application\ApplicationHandler;
+use wcf\system\cache\builder\OptionCacheBuilder;
 use wcf\system\event\EventHandler;
 use wcf\system\exception\SystemException;
 use wcf\system\exception\UserInputException;
@@ -30,7 +31,7 @@ class OptionHandler implements IOptionHandler {
 	 * cache class name
 	 * @var	string
 	 */
-	protected $cacheClass = 'wcf\system\cache\builder\OptionCacheBuilder';
+	protected $cacheClass = OptionCacheBuilder::class;
 	
 	/**
 	 * list of all option categories
@@ -378,8 +379,8 @@ class OptionHandler implements IOptionHandler {
 			return null;
 		}
 		
-		if (!is_subclass_of($className, 'wcf\system\option\IOptionType')) {
-			throw new SystemException("'".$className."' does not implement 'wcf\system\option\IOptionType'");
+		if (!is_subclass_of($className, IOptionType::class)) {
+			throw new SystemException("'".$className."' does not implement '".IOptionType::class."'");
 		}
 		
 		return $className;
diff --git a/wcfsetup/install/files/lib/system/option/user/UserOptionHandler.class.php b/wcfsetup/install/files/lib/system/option/user/UserOptionHandler.class.php
index 08ea43cca9..141e9827c3 100644
--- a/wcfsetup/install/files/lib/system/option/user/UserOptionHandler.class.php
+++ b/wcfsetup/install/files/lib/system/option/user/UserOptionHandler.class.php
@@ -5,6 +5,7 @@ use wcf\data\option\Option;
 use wcf\data\user\option\UserOption;
 use wcf\data\user\option\ViewableUserOption;
 use wcf\data\user\User;
+use wcf\system\cache\builder\UserOptionCacheBuilder;
 use wcf\system\exception\UserInputException;
 use wcf\system\option\ISearchableConditionUserOption;
 use wcf\system\option\OptionHandler;
@@ -25,7 +26,7 @@ class UserOptionHandler extends OptionHandler {
 	/**
 	 * @inheritDoc
 	 */
-	protected $cacheClass = 'wcf\system\cache\builder\UserOptionCacheBuilder';
+	protected $cacheClass = UserOptionCacheBuilder::class;
 	
 	/**
 	 * true if within registration process
diff --git a/wcfsetup/install/files/lib/system/option/user/group/UserGroupOptionHandler.class.php b/wcfsetup/install/files/lib/system/option/user/group/UserGroupOptionHandler.class.php
index 6afdf61fc6..5625f60f7a 100644
--- a/wcfsetup/install/files/lib/system/option/user/group/UserGroupOptionHandler.class.php
+++ b/wcfsetup/install/files/lib/system/option/user/group/UserGroupOptionHandler.class.php
@@ -2,6 +2,7 @@
 namespace wcf\system\option\user\group;
 use wcf\data\option\Option;
 use wcf\data\user\group\UserGroup;
+use wcf\system\cache\builder\UserGroupOptionCacheBuilder;
 use wcf\system\exception\SystemException;
 use wcf\system\exception\UserInputException;
 use wcf\system\option\OptionHandler;
@@ -21,7 +22,7 @@ class UserGroupOptionHandler extends OptionHandler {
 	/**
 	 * @inheritDoc
 	 */
-	protected $cacheClass = 'wcf\system\cache\builder\UserGroupOptionCacheBuilder';
+	protected $cacheClass = UserGroupOptionCacheBuilder::class;
 	
 	/**
 	 * user group object
@@ -83,8 +84,8 @@ class UserGroupOptionHandler extends OptionHandler {
 		if (!class_exists($className)) {
 			return null;
 		}
-		if (!is_subclass_of($className, 'wcf\system\option\user\group\IUserGroupOptionType')) {
-			throw new SystemException("'".$className."' does not implement 'wcf\system\option\user\group\IUserGroupOptionType'");
+		if (!is_subclass_of($className, IUserGroupOptionType::class)) {
+			throw new SystemException("'".$className."' does not implement '".IUserGroupOptionType::class."'");
 		}
 		
 		return $className;
diff --git a/wcfsetup/install/files/lib/system/package/PackageArchive.class.php b/wcfsetup/install/files/lib/system/package/PackageArchive.class.php
index 4ccd9547e5..9c40bb5157 100644
--- a/wcfsetup/install/files/lib/system/package/PackageArchive.class.php
+++ b/wcfsetup/install/files/lib/system/package/PackageArchive.class.php
@@ -679,7 +679,7 @@ class PackageArchive {
 			
 			// sort multiple packages by version number
 			foreach ($existingPackages as $packageName => $instances) {
-				uksort($instances, ['wcf\data\package\Package', 'compareVersion']);
+				uksort($instances, [Package::class, 'compareVersion']);
 				
 				// get package with highest version number (get last package)
 				$existingPackages[$packageName] = array_pop($instances);
diff --git a/wcfsetup/install/files/lib/system/package/PackageInstallationDispatcher.class.php b/wcfsetup/install/files/lib/system/package/PackageInstallationDispatcher.class.php
index 751a3beba1..b875a77500 100644
--- a/wcfsetup/install/files/lib/system/package/PackageInstallationDispatcher.class.php
+++ b/wcfsetup/install/files/lib/system/package/PackageInstallationDispatcher.class.php
@@ -463,7 +463,7 @@ class PackageInstallationDispatcher {
 				WHERE	languageCategory = ?";
 			$statement2 = WCF::getDB()->prepareStatement($sql);
 			$statement2->execute(['wcf.acp.package']);
-			$languageCategory = $statement2->fetchObject('wcf\data\language\category\LanguageCategory');
+			$languageCategory = $statement2->fetchObject(LanguageCategory::class);
 		}
 		else {
 			$languageCategory = LanguageFactory::getInstance()->getCategory('wcf.acp.package');
@@ -570,7 +570,7 @@ class PackageInstallationDispatcher {
 		$plugin = new $className($this, $nodeData);
 		
 		if (!($plugin instanceof IPackageInstallationPlugin)) {
-			throw new SystemException("'".$className."' does not implement 'wcf\\system\\package\\plugin\\IPackageInstallationPlugin'");
+			throw new SystemException("'".$className."' does not implement '".IPackageInstallationPlugin::class."'");
 		}
 		
 		// execute PIP
diff --git a/wcfsetup/install/files/lib/system/package/PackageInstallationScheduler.class.php b/wcfsetup/install/files/lib/system/package/PackageInstallationScheduler.class.php
index 7e638699f1..91212ae5f7 100644
--- a/wcfsetup/install/files/lib/system/package/PackageInstallationScheduler.class.php
+++ b/wcfsetup/install/files/lib/system/package/PackageInstallationScheduler.class.php
@@ -184,7 +184,7 @@ class PackageInstallationScheduler {
 				if (isset($installedPackages[$row['package']])) {
 					// package already installed -> check version
 					// sort multiple instances by version number
-					uasort($installedPackages[$row['package']], ['wcf\data\package\Package', 'compareVersion']);
+					uasort($installedPackages[$row['package']], [Package::class, 'compareVersion']);
 					
 					foreach ($installedPackages[$row['package']] as $packageID => $packageVersion) {
 						if (empty($row['minversion']) || Package::compareVersion($row['minversion'], $packageVersion, '<=')) {
@@ -481,7 +481,7 @@ class PackageInstallationScheduler {
 			
 			if (count($packageVersions) > 1) {
 				// sort by version number
-				usort($packageVersions, ['wcf\data\package\Package', 'compareVersion']);
+				usort($packageVersions, [Package::class, 'compareVersion']);
 				
 				// get highest version
 				$version = array_pop($packageVersions);
@@ -511,7 +511,7 @@ class PackageInstallationScheduler {
 		}
 		
 		// sort by version number
-		uksort($fromversions, ['wcf\data\package\Package', 'compareVersion']);
+		uksort($fromversions, [Package::class, 'compareVersion']);
 		
 		// find shortest update thread
 		$updateThread = $this->findShortestUpdateThread($package->package, $fromversions, $packageVersion, $version);
diff --git a/wcfsetup/install/files/lib/system/package/PackageUpdateDispatcher.class.php b/wcfsetup/install/files/lib/system/package/PackageUpdateDispatcher.class.php
index 36c99d60aa..6c3a478807 100644
--- a/wcfsetup/install/files/lib/system/package/PackageUpdateDispatcher.class.php
+++ b/wcfsetup/install/files/lib/system/package/PackageUpdateDispatcher.class.php
@@ -722,7 +722,7 @@ class PackageUpdateDispatcher extends SingletonFactory {
 		}
 		
 		// sort by version number
-		usort($versions, ['wcf\data\package\Package', 'compareVersion']);
+		usort($versions, [Package::class, 'compareVersion']);
 		
 		// take newest (last)
 		return array_pop($versions);
diff --git a/wcfsetup/install/files/lib/system/package/plugin/ACLOptionPackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/ACLOptionPackageInstallationPlugin.class.php
index e43139b873..2346a8b556 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/ACLOptionPackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/ACLOptionPackageInstallationPlugin.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\package\plugin;
+use wcf\data\acl\option\ACLOptionEditor;
 use wcf\system\exception\SystemException;
 use wcf\system\WCF;
 
@@ -17,7 +18,7 @@ class ACLOptionPackageInstallationPlugin extends AbstractOptionPackageInstallati
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\acl\option\ACLOptionEditor';
+	public $className = ACLOptionEditor::class;
 	
 	/**
 	 * list of loaded acl object type ids sorted by their option type name
diff --git a/wcfsetup/install/files/lib/system/package/plugin/ACPMenuPackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/ACPMenuPackageInstallationPlugin.class.php
index b45a313ef6..f2b670df83 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/ACPMenuPackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/ACPMenuPackageInstallationPlugin.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\package\plugin;
+use wcf\data\acp\menu\item\ACPMenuItemEditor;
 
 /**
  * Installs, updates and deletes ACP menu items.
@@ -15,7 +16,7 @@ class ACPMenuPackageInstallationPlugin extends AbstractMenuPackageInstallationPl
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\acp\menu\item\ACPMenuItemEditor';
+	public $className = ACPMenuItemEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/package/plugin/ACPSearchProviderPackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/ACPSearchProviderPackageInstallationPlugin.class.php
index 3f72b0e9e7..37592e27db 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/ACPSearchProviderPackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/ACPSearchProviderPackageInstallationPlugin.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\package\plugin;
+use wcf\data\acp\search\provider\ACPSearchProviderEditor;
 use wcf\system\cache\builder\ACPSearchProviderCacheBuilder;
 use wcf\system\WCF;
 
@@ -17,7 +18,7 @@ class ACPSearchProviderPackageInstallationPlugin extends AbstractXMLPackageInsta
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\acp\search\provider\ACPSearchProviderEditor';
+	public $className = ACPSearchProviderEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/package/plugin/ClipboardActionPackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/ClipboardActionPackageInstallationPlugin.class.php
index edde29ec8e..0bde28501c 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/ClipboardActionPackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/ClipboardActionPackageInstallationPlugin.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\package\plugin;
+use wcf\data\clipboard\action\ClipboardActionEditor;
 use wcf\system\WCF;
 
 /**
@@ -16,7 +17,7 @@ class ClipboardActionPackageInstallationPlugin extends AbstractXMLPackageInstall
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\clipboard\action\ClipboardActionEditor';
+	public $className = ClipboardActionEditor::class;
 	
 	/**
 	 * list of pages per action id
diff --git a/wcfsetup/install/files/lib/system/package/plugin/CoreObjectPackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/CoreObjectPackageInstallationPlugin.class.php
index 1d0d8b2a5f..11490c6c09 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/CoreObjectPackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/CoreObjectPackageInstallationPlugin.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\package\plugin;
+use wcf\data\core\object\CoreObjectEditor;
 use wcf\system\cache\builder\CoreObjectCacheBuilder;
 use wcf\system\WCF;
 
@@ -17,7 +18,7 @@ class CoreObjectPackageInstallationPlugin extends AbstractXMLPackageInstallation
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\core\object\CoreObjectEditor';
+	public $className = CoreObjectEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/package/plugin/CronjobPackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/CronjobPackageInstallationPlugin.class.php
index c575ab9462..6c44739183 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/CronjobPackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/CronjobPackageInstallationPlugin.class.php
@@ -19,7 +19,7 @@ class CronjobPackageInstallationPlugin extends AbstractXMLPackageInstallationPlu
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\cronjob\CronjobEditor';
+	public $className = CronjobEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/package/plugin/EventListenerPackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/EventListenerPackageInstallationPlugin.class.php
index e79025405a..d29d7413db 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/EventListenerPackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/EventListenerPackageInstallationPlugin.class.php
@@ -19,7 +19,7 @@ class EventListenerPackageInstallationPlugin extends AbstractXMLPackageInstallat
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\event\listener\EventListenerEditor';
+	public $className = EventListenerEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/package/plugin/ObjectTypeDefinitionPackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/ObjectTypeDefinitionPackageInstallationPlugin.class.php
index 618fdf00bf..d15d18833a 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/ObjectTypeDefinitionPackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/ObjectTypeDefinitionPackageInstallationPlugin.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\package\plugin;
+use wcf\data\object\type\definition\ObjectTypeDefinitionEditor;
 use wcf\system\WCF;
 
 /**
@@ -16,7 +17,7 @@ class ObjectTypeDefinitionPackageInstallationPlugin extends AbstractXMLPackageIn
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\object\type\definition\ObjectTypeDefinitionEditor';
+	public $className = ObjectTypeDefinitionEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/package/plugin/ObjectTypePackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/ObjectTypePackageInstallationPlugin.class.php
index f2c499b972..bf9a51315a 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/ObjectTypePackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/ObjectTypePackageInstallationPlugin.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\package\plugin;
+use wcf\data\object\type\ObjectTypeEditor;
 use wcf\system\exception\SystemException;
 use wcf\system\WCF;
 
@@ -17,7 +18,7 @@ class ObjectTypePackageInstallationPlugin extends AbstractXMLPackageInstallation
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\object\type\ObjectTypeEditor';
+	public $className = ObjectTypeEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/package/plugin/PIPPackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/PIPPackageInstallationPlugin.class.php
index 571a8a20a5..964f01e351 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/PIPPackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/PIPPackageInstallationPlugin.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\package\plugin;
+use wcf\data\package\installation\plugin\PackageInstallationPluginEditor;
 use wcf\system\WCF;
 
 /**
@@ -16,7 +17,7 @@ class PIPPackageInstallationPlugin extends AbstractXMLPackageInstallationPlugin
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\package\installation\plugin\PackageInstallationPluginEditor';
+	public $className = PackageInstallationPluginEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/package/plugin/SitemapPackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/SitemapPackageInstallationPlugin.class.php
index e812d5d942..38eedfed91 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/SitemapPackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/SitemapPackageInstallationPlugin.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\package\plugin;
+use wcf\data\sitemap\SitemapEditor;
 use wcf\system\cache\builder\SitemapCacheBuilder;
 use wcf\system\WCF;
 
@@ -17,7 +18,7 @@ class SitemapPackageInstallationPlugin extends AbstractXMLPackageInstallationPlu
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\sitemap\SitemapEditor';
+	public $className = SitemapEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/package/plugin/SmileyPackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/SmileyPackageInstallationPlugin.class.php
index 9fd2a13b60..89125f1568 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/SmileyPackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/SmileyPackageInstallationPlugin.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\package\plugin;
+use wcf\data\smiley\SmileyEditor;
 use wcf\system\WCF;
 
 /**
@@ -16,7 +17,7 @@ class SmileyPackageInstallationPlugin extends AbstractXMLPackageInstallationPlug
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\smiley\SmileyEditor';
+	public $className = SmileyEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/package/plugin/StylePackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/StylePackageInstallationPlugin.class.php
index df7eb87e51..741bb4da47 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/StylePackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/StylePackageInstallationPlugin.class.php
@@ -19,7 +19,7 @@ class StylePackageInstallationPlugin extends AbstractPackageInstallationPlugin {
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\style\StyleEditor';
+	public $className = StyleEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/package/plugin/TemplateListenerPackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/TemplateListenerPackageInstallationPlugin.class.php
index 9001aa9ccc..527d5541fb 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/TemplateListenerPackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/TemplateListenerPackageInstallationPlugin.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\package\plugin;
+use wcf\data\template\listener\TemplateListenerEditor;
 use wcf\system\cache\builder\TemplateListenerCodeCacheBuilder;
 use wcf\system\WCF;
 
@@ -17,7 +18,7 @@ class TemplateListenerPackageInstallationPlugin extends AbstractXMLPackageInstal
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\template\listener\TemplateListenerEditor';
+	public $className = TemplateListenerEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/package/plugin/UserMenuPackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/UserMenuPackageInstallationPlugin.class.php
index bddf9e2fbf..83c23c4dbc 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/UserMenuPackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/UserMenuPackageInstallationPlugin.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\package\plugin;
+use wcf\data\user\menu\item\UserMenuItemEditor;
 
 /**
  * Installs, updates and deletes user menu items.
@@ -15,7 +16,7 @@ class UserMenuPackageInstallationPlugin extends AbstractMenuPackageInstallationP
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\user\menu\item\UserMenuItemEditor';
+	public $className = UserMenuItemEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/package/plugin/UserNotificationEventPackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/UserNotificationEventPackageInstallationPlugin.class.php
index 0cf63e54d3..aa28ff0ffd 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/UserNotificationEventPackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/UserNotificationEventPackageInstallationPlugin.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\package\plugin;
+use wcf\data\user\notification\event\UserNotificationEventEditor;
 use wcf\system\exception\SystemException;
 use wcf\system\WCF;
 
@@ -17,7 +18,7 @@ class UserNotificationEventPackageInstallationPlugin extends AbstractXMLPackageI
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\user\notification\event\UserNotificationEventEditor';
+	public $className = UserNotificationEventEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/package/plugin/UserProfileMenuPackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/UserProfileMenuPackageInstallationPlugin.class.php
index ceb8bf67ba..8521a5e358 100644
--- a/wcfsetup/install/files/lib/system/package/plugin/UserProfileMenuPackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/UserProfileMenuPackageInstallationPlugin.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\package\plugin;
+use wcf\data\user\profile\menu\item\UserProfileMenuItemEditor;
 use wcf\system\WCF;
 
 /**
@@ -16,7 +17,7 @@ class UserProfileMenuPackageInstallationPlugin extends AbstractXMLPackageInstall
 	/**
 	 * @inheritDoc
 	 */
-	public $className = 'wcf\data\user\profile\menu\item\UserProfileMenuItemEditor';
+	public $className = UserProfileMenuItemEditor::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/package/validation/PackageValidationArchive.class.php b/wcfsetup/install/files/lib/system/package/validation/PackageValidationArchive.class.php
index 4d689150bb..6f17306c94 100644
--- a/wcfsetup/install/files/lib/system/package/validation/PackageValidationArchive.class.php
+++ b/wcfsetup/install/files/lib/system/package/validation/PackageValidationArchive.class.php
@@ -129,7 +129,7 @@ class PackageValidationArchive implements \RecursiveIterator {
 								WHERE	package = ?";
 							$statement = WCF::getDB()->prepareStatement($sql);
 							$statement->execute([$requirement['name']]);
-							$package = $statement->fetchObject('wcf\data\package\Package');
+							$package = $statement->fetchObject(Package::class);
 							
 							throw new PackageValidationException(PackageValidationException::MISSING_REQUIREMENT, [
 								'package' => $package,
diff --git a/wcfsetup/install/files/lib/system/poll/PollManager.class.php b/wcfsetup/install/files/lib/system/poll/PollManager.class.php
index 72d1a19569..8f2baaeb98 100644
--- a/wcfsetup/install/files/lib/system/poll/PollManager.class.php
+++ b/wcfsetup/install/files/lib/system/poll/PollManager.class.php
@@ -421,11 +421,11 @@ class PollManager extends SingletonFactory {
 		
 		// validates against object type's class
 		$className = $this->cache[$objectType]->className;
-		if (!is_subclass_of($className, 'wcf\system\poll\IPollHandler')) {
-			throw new SystemException("'".$className."' does not implement 'wcf\system\poll\IPollHandler'");
+		if (!is_subclass_of($className, IPollHandler::class)) {
+			throw new SystemException("'".$className."' does not implement '".IPollHandler::class."'");
 		}
-		else if (!is_subclass_of($className, 'wcf\system\SingletonFactory')) {
-			throw new SystemException("'".$className."' does not extend 'wcf\system\SingletonFactory'");
+		else if (!is_subclass_of($className, SingletonFactory::class)) {
+			throw new SystemException("'".$className."' does not extend '".SingletonFactory::class."'");
 		}
 		
 		$object = call_user_func([$className, 'getInstance']);
diff --git a/wcfsetup/install/files/lib/system/search/SearchEngine.class.php b/wcfsetup/install/files/lib/system/search/SearchEngine.class.php
index 5e7c2116c3..e36fcfa215 100644
--- a/wcfsetup/install/files/lib/system/search/SearchEngine.class.php
+++ b/wcfsetup/install/files/lib/system/search/SearchEngine.class.php
@@ -3,6 +3,7 @@ namespace wcf\system\search;
 use wcf\data\object\type\ObjectTypeCache;
 use wcf\system\database\util\PreparedStatementConditionBuilder;
 use wcf\system\exception\SystemException;
+use wcf\system\search\mysql\MysqlSearchEngine;
 use wcf\system\SingletonFactory;
 
 /**
@@ -84,12 +85,12 @@ class SearchEngine extends SingletonFactory implements ISearchEngine {
 					$className = '';
 				}
 			}
-				
+			
 			// fallback to MySQL
 			if (empty($className)) {
-				$className = 'wcf\system\search\mysql\MysqlSearchEngine';
+				$className = MysqlSearchEngine::class;
 			}
-				
+			
 			$this->searchEngine = call_user_func([$className, 'getInstance']);
 		}
 		
diff --git a/wcfsetup/install/files/lib/system/search/SearchIndexManager.class.php b/wcfsetup/install/files/lib/system/search/SearchIndexManager.class.php
index 5e1299b820..15706a9c4f 100644
--- a/wcfsetup/install/files/lib/system/search/SearchIndexManager.class.php
+++ b/wcfsetup/install/files/lib/system/search/SearchIndexManager.class.php
@@ -5,6 +5,7 @@ use wcf\data\object\type\ObjectTypeCache;
 use wcf\data\package\Package;
 use wcf\data\package\PackageList;
 use wcf\system\exception\SystemException;
+use wcf\system\search\mysql\MysqlSearchIndexManager;
 use wcf\system\SingletonFactory;
 
 /**
@@ -91,7 +92,7 @@ class SearchIndexManager extends SingletonFactory implements ISearchIndexManager
 			
 			// fallback to MySQL
 			if (empty($className)) {
-				$className = 'wcf\system\search\mysql\MysqlSearchIndexManager';
+				$className = MysqlSearchIndexManager::class;
 			}
 			
 			$this->searchIndexManager = call_user_func([$className, 'getInstance']);
diff --git a/wcfsetup/install/files/lib/system/search/SearchKeywordManager.class.php b/wcfsetup/install/files/lib/system/search/SearchKeywordManager.class.php
index d1670d0ee2..231d073980 100644
--- a/wcfsetup/install/files/lib/system/search/SearchKeywordManager.class.php
+++ b/wcfsetup/install/files/lib/system/search/SearchKeywordManager.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\search;
+use wcf\data\search\keyword\SearchKeyword;
 use wcf\data\search\keyword\SearchKeywordAction;
 use wcf\system\SingletonFactory;
 use wcf\system\WCF;
@@ -29,7 +30,7 @@ class SearchKeywordManager extends SingletonFactory {
 			WHERE	keyword = ?";
 		$statement = WCF::getDB()->prepareStatement($sql);
 		$statement->execute([$keyword]);
-		if (($object = $statement->fetchObject('wcf\data\search\keyword\SearchKeyword')) !== null) {
+		if (($object = $statement->fetchObject(SearchKeyword::class)) !== null) {
 			$action = new SearchKeywordAction([$object], 'update', ['data' => [
 				'searches' => $object->searches + 1,
 				'lastSearchTime' => TIME_NOW
diff --git a/wcfsetup/install/files/lib/system/search/acp/ACPSearchHandler.class.php b/wcfsetup/install/files/lib/system/search/acp/ACPSearchHandler.class.php
index a3e0941441..51f97868e1 100644
--- a/wcfsetup/install/files/lib/system/search/acp/ACPSearchHandler.class.php
+++ b/wcfsetup/install/files/lib/system/search/acp/ACPSearchHandler.class.php
@@ -51,8 +51,8 @@ class ACPSearchHandler extends SingletonFactory {
 		
 		foreach ($this->cache as $acpSearchProvider) {
 			$className = $acpSearchProvider->className;
-			if (!is_subclass_of($className, 'wcf\system\search\acp\IACPSearchResultProvider')) {
-				throw new SystemException("'".$className."' does not implement 'wcf\system\search\acp\IACPSearchResultProvider'");
+			if (!is_subclass_of($className, IACPSearchResultProvider::class)) {
+				throw new SystemException("'".$className."' does not implement '".IACPSearchResultProvider::class."'");
 			}
 			
 			$provider = new $className();
diff --git a/wcfsetup/install/files/lib/system/search/acp/AbstractCategorizedACPSearchResultProvider.class.php b/wcfsetup/install/files/lib/system/search/acp/AbstractCategorizedACPSearchResultProvider.class.php
index b5f2c8616f..bec4cad3b9 100644
--- a/wcfsetup/install/files/lib/system/search/acp/AbstractCategorizedACPSearchResultProvider.class.php
+++ b/wcfsetup/install/files/lib/system/search/acp/AbstractCategorizedACPSearchResultProvider.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\system\search\acp;
 use wcf\data\DatabaseObject;
+use wcf\data\DatabaseObjectList;
 use wcf\system\exception\SystemException;
 
 /**
@@ -89,7 +90,7 @@ abstract class AbstractCategorizedACPSearchResultProvider extends AbstractACPSea
 	 */
 	protected function loadCategories() {
 		// validate list class name
-		if (empty($this->listClassName) || !is_subclass_of($this->listClassName, 'wcf\data\DatabaseObjectList')) {
+		if (empty($this->listClassName) || !is_subclass_of($this->listClassName, DatabaseObjectList::class)) {
 			throw new SystemException("Given class '".$this->listClassName."' is empty or invalid");
 		}
 		
diff --git a/wcfsetup/install/files/lib/system/search/acp/MenuItemACPSearchResultProvider.class.php b/wcfsetup/install/files/lib/system/search/acp/MenuItemACPSearchResultProvider.class.php
index 93177e813a..8e26b833b7 100644
--- a/wcfsetup/install/files/lib/system/search/acp/MenuItemACPSearchResultProvider.class.php
+++ b/wcfsetup/install/files/lib/system/search/acp/MenuItemACPSearchResultProvider.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\search\acp;
+use wcf\data\acp\menu\item\ACPMenuItem;
 use wcf\system\database\util\PreparedStatementConditionBuilder;
 use wcf\system\menu\acp\ACPMenu;
 use wcf\system\WCF;
@@ -62,7 +63,7 @@ class MenuItemACPSearchResultProvider extends AbstractACPSearchResultProvider im
 		$statement->execute($conditions->getParameters());
 		
 		$menuItems = ACPMenu::getInstance()->menuItemList;
-		while ($menuItem = $statement->fetchObject('wcf\data\acp\menu\item\ACPMenuItem')) {
+		while ($menuItem = $statement->fetchObject(ACPMenuItem::class)) {
 			// only valid menu items exist in TreeMenu::$menuItemList,
 			// so no need to call AbstractACPSearchResultProvider::validate()
 			if (!isset($menuItems[$menuItem->menuItem])) {
diff --git a/wcfsetup/install/files/lib/system/search/acp/OptionACPSearchResultProvider.class.php b/wcfsetup/install/files/lib/system/search/acp/OptionACPSearchResultProvider.class.php
index 0a7346599e..0cb4668232 100644
--- a/wcfsetup/install/files/lib/system/search/acp/OptionACPSearchResultProvider.class.php
+++ b/wcfsetup/install/files/lib/system/search/acp/OptionACPSearchResultProvider.class.php
@@ -1,5 +1,7 @@
 <?php
 namespace wcf\system\search\acp;
+use wcf\data\option\category\OptionCategoryList;
+use wcf\data\option\Option;
 use wcf\system\cache\builder\OptionCacheBuilder;
 use wcf\system\database\util\PreparedStatementConditionBuilder;
 use wcf\system\request\LinkHandler;
@@ -19,7 +21,7 @@ class OptionACPSearchResultProvider extends AbstractCategorizedACPSearchResultPr
 	/**
 	 * @inheritDoc
 	 */
-	protected $listClassName = 'wcf\data\option\category\OptionCategoryList';
+	protected $listClassName = OptionCategoryList::class;
 	
 	/**
 	 * @inheritDoc
@@ -63,7 +65,7 @@ class OptionACPSearchResultProvider extends AbstractCategorizedACPSearchResultPr
 		
 		$optionCategories = OptionCacheBuilder::getInstance()->getData([], 'categories');
 		
-		while ($option = $statement->fetchObject('wcf\data\option\Option')) {
+		while ($option = $statement->fetchObject(Option::class)) {
 			// category is not accessible
 			if (!$this->isValid($option->categoryName)) {
 				continue;
diff --git a/wcfsetup/install/files/lib/system/search/acp/PackageACPSearchResultProvider.class.php b/wcfsetup/install/files/lib/system/search/acp/PackageACPSearchResultProvider.class.php
index 013eb70023..641565393a 100644
--- a/wcfsetup/install/files/lib/system/search/acp/PackageACPSearchResultProvider.class.php
+++ b/wcfsetup/install/files/lib/system/search/acp/PackageACPSearchResultProvider.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\search\acp;
+use wcf\data\package\Package;
 use wcf\system\database\util\PreparedStatementConditionBuilder;
 use wcf\system\request\LinkHandler;
 use wcf\system\WCF;
@@ -58,7 +59,7 @@ class PackageACPSearchResultProvider implements IACPSearchResultProvider {
 			'%'.$query.'%'
 		], $conditions->getParameters()));
 		
-		while ($package = $statement->fetchObject('wcf\data\package\Package')) {
+		while ($package = $statement->fetchObject(Package::class)) {
 			$results[] = new ACPSearchResult($package->getName(), LinkHandler::getInstance()->getLink('Package', [
 				'id' => $package->packageID,
 				'title' => $package->getName()
diff --git a/wcfsetup/install/files/lib/system/search/acp/UserACPSearchResultProvider.class.php b/wcfsetup/install/files/lib/system/search/acp/UserACPSearchResultProvider.class.php
index 441e651b08..635da14699 100644
--- a/wcfsetup/install/files/lib/system/search/acp/UserACPSearchResultProvider.class.php
+++ b/wcfsetup/install/files/lib/system/search/acp/UserACPSearchResultProvider.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\system\search\acp;
 use wcf\data\user\group\UserGroup;
+use wcf\data\user\User;
 use wcf\system\request\LinkHandler;
 use wcf\system\WCF;
 
@@ -31,7 +32,7 @@ class UserACPSearchResultProvider implements IACPSearchResultProvider {
 		$statement = WCF::getDB()->prepareStatement($sql);
 		$statement->execute([$query.'%']);
 		
-		while ($user = $statement->fetchObject('wcf\data\user\User')) {
+		while ($user = $statement->fetchObject(User::class)) {
 			if (UserGroup::isAccessibleGroup($user->getGroupIDs())) {
 				$results[] = new ACPSearchResult($user->username, LinkHandler::getInstance()->getLink('UserEdit', [
 					'object' => $user
diff --git a/wcfsetup/install/files/lib/system/search/acp/UserGroupOptionACPSearchResultProvider.class.php b/wcfsetup/install/files/lib/system/search/acp/UserGroupOptionACPSearchResultProvider.class.php
index a64e4af8f2..1c59f004f2 100644
--- a/wcfsetup/install/files/lib/system/search/acp/UserGroupOptionACPSearchResultProvider.class.php
+++ b/wcfsetup/install/files/lib/system/search/acp/UserGroupOptionACPSearchResultProvider.class.php
@@ -1,5 +1,7 @@
 <?php
 namespace wcf\system\search\acp;
+use wcf\data\user\group\option\category\UserGroupOptionCategoryList;
+use wcf\data\user\group\option\UserGroupOption;
 use wcf\system\cache\builder\UserGroupOptionCacheBuilder;
 use wcf\system\database\util\PreparedStatementConditionBuilder;
 use wcf\system\request\LinkHandler;
@@ -19,7 +21,7 @@ class UserGroupOptionACPSearchResultProvider extends AbstractCategorizedACPSearc
 	/**
 	 * @inheritDoc
 	 */
-	protected $listClassName = 'wcf\data\user\group\option\category\UserGroupOptionCategoryList';
+	protected $listClassName = UserGroupOptionCategoryList::class;
 	
 	/**
 	 * @inheritDoc
@@ -65,7 +67,7 @@ class UserGroupOptionACPSearchResultProvider extends AbstractCategorizedACPSearc
 		
 		$optionCategories = UserGroupOptionCacheBuilder::getInstance()->getData([], 'categories');
 		
-		while ($userGroupOption = $statement->fetchObject('wcf\data\user\group\option\UserGroupOption')) {
+		while ($userGroupOption = $statement->fetchObject(UserGroupOption::class)) {
 			// category is not accessible
 			if (!$this->isValid($userGroupOption->categoryName)) {
 				continue;
diff --git a/wcfsetup/install/files/lib/system/session/SessionHandler.class.php b/wcfsetup/install/files/lib/system/session/SessionHandler.class.php
index 9390e74fd7..aa421c1e85 100644
--- a/wcfsetup/install/files/lib/system/session/SessionHandler.class.php
+++ b/wcfsetup/install/files/lib/system/session/SessionHandler.class.php
@@ -6,6 +6,7 @@ use wcf\data\acp\session\virtual\ACPSessionVirtualEditor;
 use wcf\data\session\virtual\SessionVirtual;
 use wcf\data\session\virtual\SessionVirtualAction;
 use wcf\data\session\virtual\SessionVirtualEditor;
+use wcf\data\session\SessionEditor;
 use wcf\data\user\User;
 use wcf\data\user\UserEditor;
 use wcf\page\ITrackablePage;
@@ -493,7 +494,7 @@ class SessionHandler extends SingletonFactory {
 	 */
 	protected function create() {
 		$spiderID = null;
-		if ($this->sessionEditorClassName == 'wcf\data\session\SessionEditor') {
+		if ($this->sessionEditorClassName == SessionEditor::class) {
 			// get spider information
 			$spiderID = $this->getSpiderID(UserUtil::getUserAgent());
 			if ($spiderID !== null) {
diff --git a/wcfsetup/install/files/lib/system/tagging/TagEngine.class.php b/wcfsetup/install/files/lib/system/tagging/TagEngine.class.php
index 5add9f646c..a04c5422de 100644
--- a/wcfsetup/install/files/lib/system/tagging/TagEngine.class.php
+++ b/wcfsetup/install/files/lib/system/tagging/TagEngine.class.php
@@ -175,7 +175,7 @@ class TagEngine extends SingletonFactory {
 		$statement->execute($conditions->getParameters());
 		
 		$tags = [];
-		while ($tag = $statement->fetchObject('wcf\data\tag\Tag')) {
+		while ($tag = $statement->fetchObject(Tag::class)) {
 			if (!isset($tags[$tag->objectID])) {
 				$tags[$tag->objectID] = [];
 			}
diff --git a/wcfsetup/install/files/lib/system/user/authentication/DefaultUserAuthentication.class.php b/wcfsetup/install/files/lib/system/user/authentication/DefaultUserAuthentication.class.php
index 07a7928880..7f4410aaf7 100644
--- a/wcfsetup/install/files/lib/system/user/authentication/DefaultUserAuthentication.class.php
+++ b/wcfsetup/install/files/lib/system/user/authentication/DefaultUserAuthentication.class.php
@@ -34,7 +34,7 @@ class DefaultUserAuthentication extends AbstractUserAuthentication {
 	/**
 	 * @inheritDoc
 	 */
-	public function loginManually($username, $password, $userClassname = 'wcf\data\user\User') {
+	public function loginManually($username, $password, $userClassname = User::class) {
 		$user = $this->getUserByLogin($username);
 		$userSession = (get_class($user) == $userClassname ? $user : new $userClassname(null, null, $user));
 		
@@ -53,7 +53,7 @@ class DefaultUserAuthentication extends AbstractUserAuthentication {
 	/**
 	 * @inheritDoc
 	 */
-	public function loginAutomatically($persistent = false, $userClassname = 'wcf\data\user\User') {
+	public function loginAutomatically($persistent = false, $userClassname = User::class) {
 		if (!$persistent) return null;
 		
 		$user = null;
@@ -87,7 +87,7 @@ class DefaultUserAuthentication extends AbstractUserAuthentication {
 	 * @param	string		$userClassname
 	 * @return	\wcf\data\user\User
 	 */
-	protected function getUserAutomatically($userID, $password, $userClassname = 'wcf\data\user\User') {
+	protected function getUserAutomatically($userID, $password, $userClassname = User::class) {
 		$user = new $userClassname($userID);
 		if (!$user->userID || !$this->checkCookiePassword($user, $password)) {
 			$user = null;
diff --git a/wcfsetup/install/files/lib/system/user/authentication/IUserAuthentication.class.php b/wcfsetup/install/files/lib/system/user/authentication/IUserAuthentication.class.php
index aa28f3460f..f3c2061fc3 100644
--- a/wcfsetup/install/files/lib/system/user/authentication/IUserAuthentication.class.php
+++ b/wcfsetup/install/files/lib/system/user/authentication/IUserAuthentication.class.php
@@ -44,7 +44,7 @@ interface IUserAuthentication {
 	 * @param	string		$userClassname		class name of user class
 	 * @return	\wcf\data\user\User
 	 */
-	public function loginManually($username, $password, $userClassname = 'wcf\data\user\User');
+	public function loginManually($username, $password, $userClassname = User::class);
 	
 	/**
 	 * Does a user login automatically.
@@ -53,5 +53,5 @@ interface IUserAuthentication {
 	 * @param	string		$userClassname		class name of user class
 	 * @return	\wcf\data\user\User
 	 */
-	public function loginAutomatically($persistent = false, $userClassname = 'wcf\data\user\User');
+	public function loginAutomatically($persistent = false, $userClassname = User::class);
 }
diff --git a/wcfsetup/install/files/lib/system/user/authentication/UserAuthenticationFactory.class.php b/wcfsetup/install/files/lib/system/user/authentication/UserAuthenticationFactory.class.php
index 82e675631a..ebbdd448d6 100644
--- a/wcfsetup/install/files/lib/system/user/authentication/UserAuthenticationFactory.class.php
+++ b/wcfsetup/install/files/lib/system/user/authentication/UserAuthenticationFactory.class.php
@@ -19,7 +19,7 @@ class UserAuthenticationFactory extends SingletonFactory {
 	 * user authentication class name
 	 * @var	string
 	 */
-	public $className = 'wcf\system\user\authentication\DefaultUserAuthentication';
+	public $className = DefaultUserAuthentication::class;
 	
 	/**
 	 * user authentication instance
@@ -34,8 +34,8 @@ class UserAuthenticationFactory extends SingletonFactory {
 		// call loadInstance event
 		EventHandler::getInstance()->fireAction($this, 'init');
 		
-		if (!is_subclass_of($this->className, 'wcf\system\user\authentication\IUserAuthentication')) {
-			throw new SystemException("'" . $this->className . "' does not implement 'wcf\system\user\authentication\IUserAuthentication'");
+		if (!is_subclass_of($this->className, IUserAuthentication::class)) {
+			throw new SystemException("'" . $this->className . "' does not implement '".IUserAuthentication::class."'");
 		}
 		
 		$this->userAuthentication = call_user_func([$this->className, 'getInstance']);
diff --git a/wcfsetup/install/files/lib/system/user/notification/UserNotificationHandler.class.php b/wcfsetup/install/files/lib/system/user/notification/UserNotificationHandler.class.php
index 72ef8d6081..ae6358e778 100644
--- a/wcfsetup/install/files/lib/system/user/notification/UserNotificationHandler.class.php
+++ b/wcfsetup/install/files/lib/system/user/notification/UserNotificationHandler.class.php
@@ -374,7 +374,7 @@ class UserNotificationHandler extends SingletonFactory {
 		$statement->execute($conditions->getParameters());
 		
 		$notifications = [];
-		while ($notification = $statement->fetchObject('\wcf\data\user\notification\UserNotification')) {
+		while ($notification = $statement->fetchObject(UserNotification::class)) {
 			$notifications[$notification->notificationID] = $notification;
 		}
 		
diff --git a/wcfsetup/install/files/lib/system/user/notification/object/type/LikeUserNotificationObjectType.class.php b/wcfsetup/install/files/lib/system/user/notification/object/type/LikeUserNotificationObjectType.class.php
index 4986d50f42..4d85882d99 100644
--- a/wcfsetup/install/files/lib/system/user/notification/object/type/LikeUserNotificationObjectType.class.php
+++ b/wcfsetup/install/files/lib/system/user/notification/object/type/LikeUserNotificationObjectType.class.php
@@ -1,5 +1,8 @@
 <?php
 namespace wcf\system\user\notification\object\type;
+use wcf\data\like\Like;
+use wcf\data\like\LikeList;
+use wcf\system\user\notification\object\LikeUserNotificationObject;
 
 /**
  * User notification object type implementation for likes.
@@ -15,15 +18,15 @@ class LikeUserNotificationObjectType extends AbstractUserNotificationObjectType
 	/**
 	 * @inheritDoc
 	 */
-	protected static $decoratorClassName = 'wcf\system\user\notification\object\LikeUserNotificationObject';
+	protected static $decoratorClassName = LikeUserNotificationObject::class;
 	
 	/**
 	 * @inheritDoc
 	 */
-	protected static $objectClassName = 'wcf\data\like\Like';
+	protected static $objectClassName = Like::class;
 	
 	/**
 	 * @inheritDoc
 	 */
-	protected static $objectListClassName = 'wcf\data\like\LikeList';
+	protected static $objectListClassName = LikeList::class;
 }
diff --git a/wcfsetup/install/files/lib/system/user/notification/object/type/UserFollowUserNotificationObjectType.class.php b/wcfsetup/install/files/lib/system/user/notification/object/type/UserFollowUserNotificationObjectType.class.php
index 896fbc4a24..9bd4cbdc63 100644
--- a/wcfsetup/install/files/lib/system/user/notification/object/type/UserFollowUserNotificationObjectType.class.php
+++ b/wcfsetup/install/files/lib/system/user/notification/object/type/UserFollowUserNotificationObjectType.class.php
@@ -1,5 +1,8 @@
 <?php
 namespace wcf\system\user\notification\object\type;
+use wcf\data\user\follow\UserFollow;
+use wcf\data\user\follow\UserFollowList;
+use wcf\system\user\notification\object\UserFollowUserNotificationObject;
 
 /**
  * Represents a following user as a notification object type.
@@ -15,15 +18,15 @@ class UserFollowUserNotificationObjectType extends AbstractUserNotificationObjec
 	/**
 	 * @inheritDoc
 	 */
-	protected static $decoratorClassName = 'wcf\system\user\notification\object\UserFollowUserNotificationObject';
+	protected static $decoratorClassName = UserFollowUserNotificationObject::class;
 	
 	/**
 	 * @inheritDoc
 	 */
-	protected static $objectClassName = 'wcf\data\user\follow\UserFollow';
+	protected static $objectClassName = UserFollow::class;
 	
 	/**
 	 * @inheritDoc
 	 */
-	protected static $objectListClassName = 'wcf\data\user\follow\UserFollowList';
+	protected static $objectListClassName = UserFollowList::class;
 }
diff --git a/wcfsetup/install/files/lib/system/user/notification/object/type/UserProfileCommentResponseUserNotificationObjectType.class.php b/wcfsetup/install/files/lib/system/user/notification/object/type/UserProfileCommentResponseUserNotificationObjectType.class.php
index 9055ad57db..ff9995e4fd 100644
--- a/wcfsetup/install/files/lib/system/user/notification/object/type/UserProfileCommentResponseUserNotificationObjectType.class.php
+++ b/wcfsetup/install/files/lib/system/user/notification/object/type/UserProfileCommentResponseUserNotificationObjectType.class.php
@@ -1,5 +1,8 @@
 <?php
 namespace wcf\system\user\notification\object\type;
+use wcf\data\comment\response\CommentResponse;
+use wcf\data\comment\response\CommentResponseList;
+use wcf\system\user\notification\object\CommentResponseUserNotificationObject;
 
 /**
  * Represents a comment response notification object type.
@@ -15,15 +18,15 @@ class UserProfileCommentResponseUserNotificationObjectType extends AbstractUserN
 	/**
 	 * @inheritDoc
 	 */
-	protected static $decoratorClassName = 'wcf\system\user\notification\object\CommentResponseUserNotificationObject';
+	protected static $decoratorClassName = CommentResponseUserNotificationObject::class;
 	
 	/**
 	 * @inheritDoc
 	 */
-	protected static $objectClassName = 'wcf\data\comment\response\CommentResponse';
+	protected static $objectClassName = CommentResponse::class;
 	
 	/**
 	 * @inheritDoc
 	 */
-	protected static $objectListClassName = 'wcf\data\comment\response\CommentResponseList';
+	protected static $objectListClassName = CommentResponseList::class;
 }
diff --git a/wcfsetup/install/files/lib/system/user/notification/object/type/UserProfileCommentUserNotificationObjectType.class.php b/wcfsetup/install/files/lib/system/user/notification/object/type/UserProfileCommentUserNotificationObjectType.class.php
index 008259112d..50af651f90 100644
--- a/wcfsetup/install/files/lib/system/user/notification/object/type/UserProfileCommentUserNotificationObjectType.class.php
+++ b/wcfsetup/install/files/lib/system/user/notification/object/type/UserProfileCommentUserNotificationObjectType.class.php
@@ -1,5 +1,8 @@
 <?php
 namespace wcf\system\user\notification\object\type;
+use wcf\data\comment\Comment;
+use wcf\data\comment\CommentList;
+use wcf\system\user\notification\object\CommentUserNotificationObject;
 use wcf\system\WCF;
 
 /**
@@ -16,17 +19,17 @@ class UserProfileCommentUserNotificationObjectType extends AbstractUserNotificat
 	/**
 	 * @inheritDoc
 	 */
-	protected static $decoratorClassName = 'wcf\system\user\notification\object\CommentUserNotificationObject';
+	protected static $decoratorClassName = CommentUserNotificationObject::class;
 	
 	/**
 	 * @inheritDoc
 	 */
-	protected static $objectClassName = 'wcf\data\comment\Comment';
+	protected static $objectClassName = Comment::class;
 	
 	/**
 	 * @inheritDoc
 	 */
-	protected static $objectListClassName = 'wcf\data\comment\CommentList';
+	protected static $objectListClassName = CommentList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/worker/AbstractRebuildDataWorker.class.php b/wcfsetup/install/files/lib/system/worker/AbstractRebuildDataWorker.class.php
index 87ee03661e..23b38ed30d 100644
--- a/wcfsetup/install/files/lib/system/worker/AbstractRebuildDataWorker.class.php
+++ b/wcfsetup/install/files/lib/system/worker/AbstractRebuildDataWorker.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\worker;
+use wcf\data\DatabaseObjectList;
 use wcf\system\event\EventHandler;
 use wcf\system\exception\SystemException;
 use wcf\system\request\LinkHandler;
@@ -91,8 +92,8 @@ abstract class AbstractRebuildDataWorker extends AbstractWorker implements IRebu
 			throw new SystemException('DatabaseObjectList class name not specified.');
 		}
 		
-		if (!is_subclass_of($this->objectListClassName, 'wcf\data\DatabaseObjectList')) {
-			throw new SystemException("'".$this->objectListClassName."' does not extend 'wcf\data\DatabaseObjectList'");
+		if (!is_subclass_of($this->objectListClassName, DatabaseObjectList::class)) {
+			throw new SystemException("'".$this->objectListClassName."' does not extend '".DatabaseObjectList::class."'");
 		}
 		
 		$this->objectList = new $this->objectListClassName();
diff --git a/wcfsetup/install/files/lib/system/worker/AttachmentRebuildDataWorker.class.php b/wcfsetup/install/files/lib/system/worker/AttachmentRebuildDataWorker.class.php
index 659cae2d11..a04242082e 100644
--- a/wcfsetup/install/files/lib/system/worker/AttachmentRebuildDataWorker.class.php
+++ b/wcfsetup/install/files/lib/system/worker/AttachmentRebuildDataWorker.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\system\worker;
 use wcf\data\attachment\AttachmentAction;
+use wcf\data\attachment\AttachmentList;
 use wcf\system\exception\SystemException;
 
 /**
@@ -17,7 +18,7 @@ class AttachmentRebuildDataWorker extends AbstractRebuildDataWorker {
 	/**
 	 * @inheritDoc
 	 */
-	protected $objectListClassName = 'wcf\data\attachment\AttachmentList';
+	protected $objectListClassName = AttachmentList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/worker/LikeRebuildDataWorker.class.php b/wcfsetup/install/files/lib/system/worker/LikeRebuildDataWorker.class.php
index b8bd7acd68..60db543e5f 100644
--- a/wcfsetup/install/files/lib/system/worker/LikeRebuildDataWorker.class.php
+++ b/wcfsetup/install/files/lib/system/worker/LikeRebuildDataWorker.class.php
@@ -1,6 +1,7 @@
 <?php
 namespace wcf\system\worker;
 use wcf\data\like\Like;
+use wcf\data\like\LikeList;
 use wcf\system\user\activity\point\UserActivityPointHandler;
 use wcf\system\WCF;
 
@@ -18,7 +19,7 @@ class LikeRebuildDataWorker extends AbstractRebuildDataWorker {
 	/**
 	 * @inheritDoc
 	 */
-	protected $objectListClassName = 'wcf\data\like\LikeList';
+	protected $objectListClassName = LikeList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/worker/LikeUserRebuildDataWorker.class.php b/wcfsetup/install/files/lib/system/worker/LikeUserRebuildDataWorker.class.php
index bce556418c..1fde8d86b4 100644
--- a/wcfsetup/install/files/lib/system/worker/LikeUserRebuildDataWorker.class.php
+++ b/wcfsetup/install/files/lib/system/worker/LikeUserRebuildDataWorker.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\worker;
+use wcf\data\like\object\LikeObjectList;
 use wcf\data\like\Like;
 use wcf\system\database\util\PreparedStatementConditionBuilder;
 use wcf\system\WCF;
@@ -18,7 +19,7 @@ class LikeUserRebuildDataWorker extends AbstractRebuildDataWorker {
 	/**
 	 * @inheritDoc
 	 */
-	protected $objectListClassName = 'wcf\data\like\object\LikeObjectList';
+	protected $objectListClassName = LikeObjectList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/system/worker/SendNewPasswordWorker.class.php b/wcfsetup/install/files/lib/system/worker/SendNewPasswordWorker.class.php
index e4e4e3a600..e8e5fd5cd4 100644
--- a/wcfsetup/install/files/lib/system/worker/SendNewPasswordWorker.class.php
+++ b/wcfsetup/install/files/lib/system/worker/SendNewPasswordWorker.class.php
@@ -41,7 +41,7 @@ class SendNewPasswordWorker extends AbstractWorker {
 	 */
 	public function execute() {
 		$userList = new UserList();
-		$userList->decoratorClassName = 'wcf\data\user\UserEditor';
+		$userList->decoratorClassName = UserEditor::class;
 		$userList->getConditionBuilder()->add('user_table.userID IN (?)', [$this->parameters['userIDs']]);
 		$userList->sqlLimit = $this->limit;
 		$userList->sqlOffset = $this->limit * $this->loopCount;
diff --git a/wcfsetup/install/files/lib/system/worker/UserRebuildDataWorker.class.php b/wcfsetup/install/files/lib/system/worker/UserRebuildDataWorker.class.php
index c2f2130206..95167f4b67 100644
--- a/wcfsetup/install/files/lib/system/worker/UserRebuildDataWorker.class.php
+++ b/wcfsetup/install/files/lib/system/worker/UserRebuildDataWorker.class.php
@@ -2,6 +2,7 @@
 namespace wcf\system\worker;
 use wcf\data\like\Like;
 use wcf\data\user\UserEditor;
+use wcf\data\user\UserList;
 use wcf\data\user\UserProfileAction;
 use wcf\system\database\util\PreparedStatementConditionBuilder;
 use wcf\system\user\activity\point\UserActivityPointHandler;
@@ -21,7 +22,7 @@ class UserRebuildDataWorker extends AbstractRebuildDataWorker {
 	/**
 	 * @inheritDoc
 	 */
-	protected $objectListClassName = 'wcf\data\user\UserList';
+	protected $objectListClassName = UserList::class;
 	
 	/**
 	 * @inheritDoc
diff --git a/wcfsetup/install/files/lib/util/HeaderUtil.class.php b/wcfsetup/install/files/lib/util/HeaderUtil.class.php
index f76d29829e..13244aee78 100644
--- a/wcfsetup/install/files/lib/util/HeaderUtil.class.php
+++ b/wcfsetup/install/files/lib/util/HeaderUtil.class.php
@@ -81,7 +81,7 @@ final class HeaderUtil {
 			@header('X-Frame-Options: SAMEORIGIN');
 		}
 		
-		ob_start(['wcf\util\HeaderUtil', 'parseOutput']);
+		ob_start([self::class, 'parseOutput']);
 	}
 	
 	/**
@@ -120,7 +120,7 @@ final class HeaderUtil {
 		// 3rd party plugins may differ the actual output before it is sent to the browser
 		// please be aware, that $eventObj is not available here due to this being a static
 		// class. Use HeaderUtil::$output to modify it.
-		if (!defined('NO_IMPORTS')) EventHandler::getInstance()->fireAction('wcf\util\HeaderUtil', 'parseOutput');
+		if (!defined('NO_IMPORTS')) EventHandler::getInstance()->fireAction(self::class, 'parseOutput');
 		
 		// gzip compression
 		if (self::$enableGzipCompression) {
-- 
2.20.1