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HomeBackend DevelopmentPHP TutorialPHP类方法重写原则

可能我们日常工作中很少用到这块知识点,但我还是喜欢把遇到的却不清楚的知识点摸清

PHP的类方法重写规则

1、final修饰的类方法不可被子类重写 即便final private方法无法被继承 子类仍不能对齐进行重写

class FinalMethod{    //可继承不可重写    final public function finalPublic()    {        echo "can be inherited, but be overrided";    }    //可继承不可重写    final protected function finalProtected()    {        echo "can be inherited, but be overrided";    }    //不可继承不可重写 虽然子类继承不到父类的private方法 但同时也会被final限制无法重写    final private function finalPrivate()    {        echo "can not be inherited or be overrided";    }    //虽然不可继承 但子类里可重写此方法    private function private()    {        echo "can not be inherited ,but be overrided";    }}class Override extends FinalMethod{    //error    public function finalPublic()    {     }    //error    protected function finalProtected()    {    }    //error    private function finalPrivate()    {    }    //correct    public/protected/private function private()    {        //子类继承父类重写父类方法时访问级别只能更加宽松 不可更为严格    }}

2、PHP无重载机制 所以判断是不是重写只会通过方法名(C/C++不仅要方法名相同,参数也相同时才被视为重写,否则即为重载,即新定义了一个多态函数的态)

class Father{    public function index($args_1)    {    }}class Child extends Father{    public function index($args_1, $args_2)    {        //在C/C++中此为重载非重写,因为C/C++具有标准的多态机制,会因参数不同而视为某一方法的另一种态        //but在php中此依然为重写    }        private function index($args_1, $args_2)    {        //C/C++会因为参数不同于父类方法而视为重载,即新定义了一个函数的态,所以不会受到继承访问权限的限制        //但php仍然会被视为对父类方法的重写,会受到访问权限的控制    }}

3、重写时访问级别只可以等于或者宽松于父类,不可提升访问级别,即父类的public方法不能被子类重写为protected或者private,protected方法不能被重写为private,可以宽松er,不可以严格er

class Father{    public function index()    {    }}class Child extends Father{    protected/private function index()    {       //访问权限提升 错误        //父类为public 则子类重写也只能为public       //父类为protected 则子类可为public/protected       //父类为private 则子类public/protected/private皆可    }}


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