Php/docs/language.attributes.classes
Declaring Attribute Classes
While not strictly required it is recommended to create an actual class for every attribute.
In the most simple case only an empty class is needed with the #[Attribute] attribute declared
that can be imported from the global namespace with a use statement.
Example #1 Using target specification to restrict where attributes can be used
<?phpnamespace Example;use Attribute;#[Attribute]class MyAttribute{}
To restrict the type of declaration an attribute can be assigned to, a bitmask can be passed as the first
argument to the #[Attribute] declaration.
Example #2 Simple Attribute Class
<?phpnamespace Example;use Attribute;#[Attribute(Attribute::TARGET_METHOD | Attribute::TARGET_FUNCTION)]class MyAttribute{}
Declaring MyAttribute on another type will now throw an exception during the call to ReflectionAttribute::newInstance()
By default an attribute can only be used once per declaration. If the attribute should be repeatable on declarations it must
be specified as part of the bitmask to the #[Attribute] declaration.
Example #3 Using IS_REPEATBLE to allow attribute on a declaration multiple times
<?phpnamespace Example;use Attribute;#[Attribute(Attribute::TARGET_METHOD | Attribute::TARGET_FUNCTION | Attribute::IS_REPEATABLE)]class MyAttribute{}
