PHP从父级访问子级的受保护值

Question

我有这段代码，我想在父级和子级中进行方法抽象，以定义属性

class SuperClass{
    static protected $message = "This is the parent";

    public static function showMessage(){
        echo self::$message."<br/>";
    }
}

class SubClass1 extends SuperClass {
    static protected $message = "This is the first child";

}

class SubClass2 extends SuperClass {
    static protected $message = "This is the second child";
}

SuperClass::showMessage();
SubClass1::showMessage();
SubClass2::showMessage();

我希望看到

This is the parent
This is the first child
This is the second child

但是我得到的是

This is the parent
This is the parent
This is the parent

Answer 1

这是后期静态绑定的非常经典的用例。 只需将父类中的关键字“ self”替换为“ static”

class SuperClass{
    static protected $message = "This is the parent";

    public static function showMessage(){
        echo static::$message."<br/>";
    }
}

这将适用于PHP 5.3+