+#### `ICssClassFormField`
+
+!!! info "Only available since version 5.4."
+
+`ICssClassFormField` has to be implemented by form fields for which CSS classes can be added to the actual form element (in addition to adding CSS classes to the surrounding element via the class-related methods of `IFormNode`).
+The implementing class has to implement the methods `addFieldClass(string $class): self`/`addFieldClasses(array $classes): self` and `getFieldClasses(): array`, which are used to add and get the CSS classes, respectively.
+Additionally, `hasFieldClass(string $class): bool` has to implemented to check if a certain CSS class is present and `removeFieldClass(string $class): self` to remove a CSS class.
+`TCssClassFormField` provides a default implementation of these methods.
+
+