$this是什么意思 [英] What is the meaning of $this

问题描述

我看到一些脚本在具有 OOP 的 PHP 脚本中包含 $this，我从来不知道它的含义......就像

I've seen some scripts contain $this in a PHP script that has OOP, I never knew the meaning of it... like

$this->refresh();

也许可以向我解释一下 $this 指的是什么...?

Perhaps explain to me what $this refers to be...?

但我知道你不能像 $this_is_a_variable 那样将它用作动态变量，但为什么不能将它用作动态变量呢?

But I do know that you cannot use it as a dynamic variable like $this_is_a_variable but why can't use it as a dynamic variable?

推荐答案

$this 是对当前对象的引用.

$this is a reference to the current object.

只能在类方法中使用.

来自手册:

伪变量 $this 在对象上下文中调用方法时可用.$this 是对调用对象的引用(通常是该方法所属的对象，但也可能是另一个对象，如果该方法是从辅助对象的上下文中静态调用的).

The pseudo-variable $this is available when a method is called from within an object context. $this is a reference to the calling object (usually the object to which the method belongs, but possibly another object, if the method is called statically from the context of a secondary object).

一个简单的现实世界示例:

a simple real world example:

class Classname
{
  private $message = "The big brown fox... jumped....";

  function setMessage($givenMessage) {
    $this->message = $givenMessage;
  }

  function getMessage() {
    return $this->message;  // Will output whatever value 
                            // the object's message variable was set to
  }
}

$my_object = new Classname();  // this is a valid object
echo $my_object->getMessage();  // Will output "The big brown fox... jumped...."

$my_object->setMessage("Hello World!");
echo $my_object->getMessage();  // Will output "Hello world"

$this 在静态上下文中调用方法时不可用:

$this is not available when you call a method in a static context:

Classname::showMessage(); // Will throw an error: 
                          // `$this` used while not in object context

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