It is recommended to define a separate class for each attribute. In the simplest
case, an empty class with the #[Attribute] declaration is sufficient.
The attribute can be imported from the global namespace using a use
statement.
Example #1 Simple Attribute Class
<?php
namespace Example;
use Attribute;
#[Attribute]
class MyAttribute
{
}
To restrict the types of declarations an attribute can be applied to,
pass a bitmask as the first argument to the #[Attribute]
declaration.
Example #2 Using target specification to restrict where attributes can be used
<?php
namespace 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()
The following targets can be specified:
Attribute::TARGET_CLASSAttribute::TARGET_FUNCTIONAttribute::TARGET_METHODAttribute::TARGET_PROPERTYAttribute::TARGET_CLASS_CONSTANTAttribute::TARGET_PARAMETERAttribute::TARGET_ALL
By default, an attribute can only be used once per declaration. To allow
an attribute to be repeatable, specify it in the bitmask of the
#[Attribute] declaration using the
Attribute::IS_REPEATABLE flag.
Example #3 Using IS_REPEATABLE to allow attribute on a declaration multiple times
<?php
namespace Example;
use Attribute;
#[Attribute(Attribute::TARGET_METHOD | Attribute::TARGET_FUNCTION | Attribute::IS_REPEATABLE)]
class MyAttribute
{
}