self和$ this->之间的区别在哪里?在一个PHP类或PHP方法? [英] Where's the difference between self and $this-> in a PHP class or PHP method?

问题描述

PHP类或PHP方法中self和$this->之间的区别是什么?

Where's the difference between self and $this-> in a PHP class or PHP method?

示例:

我最近看过这段代码.

I've seen this code recently.

public static function getInstance() {

    if (!self::$instance) {
        self::$instance = new PDO("mysql:host='localhost';dbname='animals'", 'username', 'password');;
        self::$instance-> setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    }
    return self::$instance;
}

但是我记得$this->指向一个类的当前实例(对象)(可能也是错误的).但是，有什么区别?

But I remember that $this-> refers to the current instance (object) of a class (might also be wrong). However, what's the difference?

推荐答案

$this引用该类的实例，这是正确的.但是，还有一种叫做静态的东西，对于该类的所有实例都是相同的. self::是这些属性和功能的访问器.

$this refers to the instance of the class, that is correct. However, there is also something called static state, which is the same for all instances of that class. self:: is the accessor for those attributes and functions.

此外，您通常不能从静态方法访问实例成员.意思是，您不能

Also, you cannot normally access an instance member from a static method. Meaning, you cannot do

static function something($x) {
  $this->that = $x;
}

因为静态方法不会知道您要引用哪个实例.

because the static method would not know which instance you are referring to.

这篇关于self和$ this->之间的区别在哪里?在一个PHP类或PHP方法?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！