什么是:: class在PHP中? [英] What is ::class in PHP?

问题描述

PHP中的::class表示法是什么?

What is the ::class notation in PHP?

由于语法的本质，快速的Google搜索不会返回任何内容.

A quick Google search returns nothing because of the nature of the syntax.

冒号类

使用这种表示法有什么好处?

What's the advantage of using this notation?

protected $commands = [
    \App\Console\Commands\Inspire::class,
];

推荐答案

此功能已在PHP 5.5中实现.

This feature was implemented in PHP 5.5.

文档: http://php.net/manual/en/migration55.new-features.php#migration55.new-features.class-name

这非常有用，有两个原因.

It's very useful for 2 reasons.

• 您不必再将类名存储在字符串中.因此，当您重构代码时，许多IDE都可以检索这些类名称.
• 您可以使用use关键字来解析您的课程，而无需编写完整的课程名称.

• You don't have to store your class names in strings anymore. So, many IDEs can retrieve these class names when you refactor your code
• You can use the use keyword to resolve your class and you don't need to write the full class name.

例如:

use \App\Console\Commands\Inspire;

//...

protected $commands = [
    Inspire::class, // Equivalent to "App\Console\Commands\Inspire"
];

更新:

此功能对于 后期静态绑定也很有用 .

This feature is also useful for Late Static Binding.

您可以使用static::class功能而不是使用__CLASS__魔术常数来获取父类内部的派生类的名称.例如:

Instead of using the __CLASS__ magic constant, you can use the static::class feature to get the name of the derived class inside the parent class. For example:

class A {

    public function getClassName(){
        return __CLASS__;
    }

    public function getRealClassName() {
        return static::class;
    }
}

class B extends A {}

$a = new A;
$b = new B;

echo $a->getClassName();      // A
echo $a->getRealClassName();  // A
echo $b->getClassName();      // A
echo $b->getRealClassName();  // B

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