thinkphp5.1中的单例模式

//thinkphp5.1中的单例模式

class Demo

{

    private function __construct(){}

    private function __clone(){}

    protected static $instance=null;

    public static function getConnect(){

       if(is_null(static::$instance)){

           static::$instance=new static();

         }

        return static::$instance;

     }

}

$connect=Demo::getConnect();