Attribute syntax
There are several parts to the attributes syntax. First, an attribute
declaration is always enclosed with a starting
#[
and a corresponding ending
]
. Inside, one or many attributes are listed,
separated by comma. The attribute name is an unqualified, qualified
or fully-qualified name as described in Using Namespaces Basics.
Arguments to the attribute are optional, but are enclosed in the usual parenthesis ()
.
Arguments to attributes can only be literal values or constant expressions. Both positional and
named arguments syntax can be used.
Attribute names and their arguments are resolved to a class and the arguments are passed to its constructor, when an instance of the attribute is requested through the Reflection API. As such a class should be introduced for each attribute.
Beispiel #1 Attribute Syntax
<?php
// a.php
namespace MyExample;
use Attribute;
#[Attribute]
class MyAttribute
{
const VALUE = 'value';
private $value;
public function __construct($value = null)
{
$this->value = $value;
}
}
// b.php
namespace Another;
use MyExample\MyAttribute;
#[MyAttribute]
#[\MyExample\MyAttribute]
#[MyAttribute(1234)]
#[MyAttribute(value: 1234)]
#[MyAttribute(MyAttribute::VALUE)]
#[MyAttribute(array("key" => "value"))]
#[MyAttribute(100 + 200)]
class Thing
{
}
#[MyAttribute(1234), MyAttribute(5678)]
class AnotherThing
{
}