Review PHP设计模式之——单例模式

单例模式：

 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();