Attribute syntax consists of several key components. An attribute
declaration starts with #[ and ends with
]. Inside, one or more attributes can be listed,
separated by commas. The attribute name can be unqualified, qualified,
or fully-qualified, as described in Using Namespaces Basics.
Arguments to the attribute are optional and enclosed in parentheses
(). Arguments can only be literal values or constant
expressions. Both positional and named argument syntax are supported.
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. Therefore, it is recommended to introduce a class for each attribute.
Example #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
{
}It wasn't obvious to me for a while but you can subclass attributes
https://3v4l.org/TrMTe
<?php
#[Attribute(Attribute::TARGET_PROPERTY)]
class PropertyAttributes
{
public function __construct(
public readonly ?string $name = null,
public readonly ?string $label = null,
) {}
}
#[Attribute(Attribute::TARGET_PROPERTY)]
class IntegerPropertyAttributes extends PropertyAttributes
{
public function __construct(
?string $name = null,
?string $label = null,
public readonly ?int $default = null,
public readonly ?int $min = null,
public readonly ?int $max = null,
public readonly ?int $step = null,
) {
parent::__construct($name, $label);
}
}
#[Attribute(Attribute::TARGET_PROPERTY)]
class FloatPropertyAttributes extends PropertyAttributes
{
public function __construct(
?string $name = null,
?string $label = null,
public readonly ?float $default = null,
public readonly ?float $min = null,
public readonly ?float $max = null,
) {
parent::__construct($name, $label);
}
}
class MyClass
{
#[IntegerPropertyAttributes('prop', 'property: ', 5, 0, 10, 1)]
public int $prop;
}
$refl = new ReflectionProperty('MyClass', 'prop');
$attributes = $refl->getAttributes();
foreach ($attributes as $attribute) {
var_dump($attribute->getName());
var_dump($attribute->getArguments());
var_dump($attribute->newInstance());
}
?>