PHP Interview Questions and answers

E_DEPRECATED

The E_DEPRECATED error level is used to indicate that a function or feature has been deprecated.

E_USER_DEPRECATED

The E_USER_DEPRECATED level is intended for indicating deprecated features in user code, similarly to the E_USER_ERROR and E_USER_WARNING levels.

class A {
    public function who() {
        echo __CLASS__;
    }
    public function test() {
        $this->who();
    }
}

class B extends A {
    public function who() {
        echo __CLASS__;
    }
}
$obj = new B;
$obj->test();

Out put of the above snippet is? B This is mainly because we have the object instance named as $this is for the class B, though the function is instantiated inside class A. But, If you need the expected output which is “A”, we can call them statically as follows

class A {
    public static function who() {
        echo __CLASS__;
    }
    public static function test() {
        self::who();
    }
}

class B extends A {
    public static function who() {
        echo __CLASS__;
    }
}

B::test();

Out put -> A

Main limitation of self:: or __CLASS__ are resolved using the class in which the function belongs, as in where it was defined. By introducing late static binding this limitation has been resolved as follows,

class A {
    public static function who() {
        echo __CLASS__;
    }
    public static function test() {
        static::who(); // Here comes Late Static Bindings
    }
}

class B extends A {
    public static function who() {
        echo __CLASS__;
    }
}

B::test();

Out put -> B