PHP 中的 ::class 是什么？
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What is ::class in PHP?
提问by Yada
What is the ::classnotation in PHP?
::classPHP 中的符号是什么？
A quick Google search returns nothing because of the nature of the syntax.
由于语法的性质，快速的 Google 搜索不会返回任何内容。
colon colon class
冒号类
What's the advantage of using this notation?
使用这个符号有什么好处？
protected $commands = [
\App\Console\Commands\Inspire::class,
];
回答by alphayax
This feature was implemented in PHP 5.5.
这个特性是在 PHP 5.5 中实现的。
Documentation : http://php.net/manual/en/migration55.new-features.php#migration55.new-features.class-name
文档：http: //php.net/manual/en/migration55.new-features.php#migration55.new-features.class-name
It's very useful for 2 reasons.
它非常有用有两个原因。
- 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
usekeyword to resolve your class and you don't need to write the full class name.
- 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 可以检索这些类名
- 您可以使用
use关键字来解析您的类，而无需编写完整的类名。
For exemple :
举个例子 ：
use \App\Console\Commands\Inspire;
//...
protected $commands = [
Inspire::class, // Equivalent to "App\Console\Commands\Inspire"
];
Update:
更新：
This feature is also useful for Late Static Binding.
此功能对于后期静态绑定也很有用。
Instead of using the __CLASS__magic constant, you can use the static::classfeature to get the name of the derived class inside the parent class. For example:
__CLASS__您可以使用该static::class功能来获取父类中派生类的名称，而不是使用魔术常量。例如：
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 $b->getRealClassName(); // B
回答by xdazz
classis special, which is provided by php to get the fully qualified class name.
class是特殊的，由 php 提供，用于获取完全限定的类名。
See http://php.net/manual/en/migration55.new-features.php#migration55.new-features.class-name.
请参阅http://php.net/manual/en/migration55.new-features.php#migration55.new-features.class-name。
<?php
class foo {
const test = 'foobar!';
}
echo foo::test; // print foobar!
回答by Lucas Bustamante
If you're curious in which category ::classfalls into, (whether it's a language construct, etc), it's very simple. It's a constant. PHP calls it a "Special Constant". It's special because it's provided by PHP.
如果您想知道::class属于哪个类别（无论是语言结构等），这很简单。这是一个常数。PHP 称之为“特殊常量”。它很特别，因为它是由 PHP 提供的。
回答by Harald Witt
Please be aware to use the following:
请注意使用以下内容：
if ($whatever instanceof static::class) {...}
This will throw a syntax error:
这将引发语法错误：
unexpected 'class' (T_CLASS), expecting variable (T_VARIABLE) or '$'
unexpected 'class' (T_CLASS), expecting variable (T_VARIABLE) or '$'
But you can do the following instead:
但您可以改为执行以下操作：
if ($whatever instanceof static) {...}
or
或者
$class = static::class;
if ($whatever instanceof $class) {...}
