PHP中$this、self的理解附带范围解析操作符::（摘自官网）

原创于 2019-04-26 14:55:50 发布 · 1.1k 阅读

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本文探讨了PHP中self关键字与$this变量的区别。self指向调用它的类，而$this指向当前对象的类。通过示例代码说明，在继承情况下，self::方法名将调用父类方法，不受子类覆盖影响；而$this->方法名则调用当前对象所属类的方法，允许子类覆盖。

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In PHP, you use the self keyword to access static properties and methods.

The problem is that you can replace $this->method() with self::method() anywhere, regardless if method() is declared static or not. So which one should you use?

Consider this code:

class ParentClass {
    function test() {
        self::who();    // will output 'parent'
        $this->who();    // will output 'child'
    }

    function who() {
        echo 'parent';
    }
}

class ChildClass extends ParentClass {
    function who() {
        echo 'child';
    }
}

$obj = new ChildClass();
$obj->test();
In this example, self::who() will always output ‘parent’, while $this->who() will depend on what class the object has.

Now we can see that self refers to the class in which it is called, while $this refers to the class of the current object.

So, you should use self only when $this is not available, or when you don’t want to allow descendant classes to overwrite the current method.