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();