Attributes
PHP Manual

Declaring Attribute Classes

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_CLASS
  • Attribute::TARGET_FUNCTION
  • Attribute::TARGET_METHOD
  • Attribute::TARGET_PROPERTY
  • Attribute::TARGET_CLASS_CONSTANT
  • Attribute::TARGET_PARAMETER
  • Attribute::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
{
}