PHP: 注解语法

注解语法

注解语法由几个关键组件组成。属性声明以 #[ 开始，以 ] 结束。内部可以列出一个或多个注解，注解之间用逗号分隔。注解名称如使用命名空间基础中所述，可以是未限定、限定或完全限定的。注解的参数是可选的，并用圆括号 () 括起来。参数只能是字面值或常量表达式，同时支持位置参数和命名参数语法。

注解名称及其参数会解析为类，并在通过反射 API 请求注解实例时，将参数传递给其构造方法。因此，建议为每个注解都引入对应的类。

示例 #1 注解语法

<?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
{
}

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yarns dot purport0n at icloud dot com ¶

1 year ago

It wasn't obvious to me for a while but you can subclass attributeshttps://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());    }?>