Implementation Of Singleton Design Pattern in PHP

<?php

/*
 *
 * @Author: Zuhair Mirza
 * @Implementation Of Singleton Design Pattern in PHP
 * @Date : 12-June-2015
 * @Defination  : In software engineering, the singleton pattern is a design pattern that
 * restricts the instantiation of a class to one object. This is useful when exactly one
 * object is needed to coordinate actions across the system.
 */

class Singleton {

    /**
     * Returns the *Singleton* instance of this class.
     *
     * @staticvar Singleton $instance The *Singleton* instances of this class.
     *
     * @return Singleton The *Singleton* instance.
     */
    public static function getInstance() {
        static $instance = null;

        if (null === $instance) {
            $instance = new static();
        }

        return $instance;
    }

    protected function __construct() {
       
    }

    private function __clone() {
       
    }

    private function __wakeup() {
       
    }

}

class SingletonChild extends Singleton {
   
}

$obj = Singleton::getInstance();

var_dump($obj === Singleton::getInstance());             // Output : bool(true)

$anotherObj = SingletonChild::getInstance();

var_dump($anotherObj === Singleton::getInstance());      // Output : bool(false)

var_dump($obj === Singleton::getInstance());             // Output : bool(true)