class Single {

     private static $_instance;

     private function __construct(){

         //define method as private

     }

     public function __clone(){

         trigger_error('Clone is not allow!', E_USER_ERROR);

     }

     public static function getInstance(){

         if(!(self::$_instance instanceof self)){

             self::$_instance = new self;

         }

         return self::$_instance;

     }

     public function show(){

         phpinfo();

     }

 }

 $single = Single::getInstance();

 $single->show();