1 class Single { 2     private static $_instance; 3  4     private function __construct(){ 5         //define method as private 6     } 7  8     public function __clone(){ 9         trigger_error('Clone is not allow!', E_USER_ERROR);10     }11 12     public static function getInstance(){13         if(!(self::$_instance instanceof self)){14             self::$_instance = new self;15         }16         return self::$_instance;17     }18 19     public function show(){20         phpinfo();21     }22 }23 $single = Single::getInstance();24 $single->show();