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.

    Приклад #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.

    Приклад #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:

    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.

    Приклад #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
    {
    }

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    User Contributed Notes 1 note

    up
    13
    esdras-schonevald
    3 years ago
    #! Require PHP >= 8.0

    #! This is a Sample

    <?php

    declare(strict_types = 1);

    #[    Attribute]
    class     Foo
    {
    function     __construct(){
    echo     "Running " . __METHOD__ . PHP_EOL;
    }
    }

    #[    Attribute(Attribute::TARGET_CLASS|Attribute::IS_REPEATABLE)]
    class     Bar {
    function     __construct(?string ...$args){
    echo     "Running " . __METHOD__ ,
    " args: " . implode(", ", $args) . PHP_EOL;
    }
    }

    #[    Attribute(Attribute::TARGET_ALL)]
    class     Baz {
    function     __construct(
    private     string $parameter
    ){
    echo     "Running " . __METHOD__ ,
    " arg: " . $this->parameter . PHP_EOL;
    }
    }

    #[    Foo] // [0]
    #[Bar] // [1]
    #[Bar("Banana")] // [2]
    #[Bar("Banana", "Apple", "Lemon", "Grape")] // [3]
    #[Baz("The Only One")] // [4]
    class Qux
    {
    }

    // Getting class attribute with ReflectionClass
    $ref = new ReflectionClass(Qux::class);
    $attrs = $ref->getAttributes(); // Array of attributes

    $attrs[0]->newInstance(); // "Running Foo::__construct"
    $attrs[1]->newInstance(); // "Running Bar::__construct args: "
    $attrs[2]->newInstance(); // "Running Bar::__construct args: Banana"
    $attrs[3]->newInstance(); // "Running Bar::__construct args: Banana, Apple, Lemon, Grape"
    $attrs[4]->newInstance(); // "Running Baz::__construct arg: The Only One"
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