PHP原生連接數據庫和查詢

public function  Test()
    {
//        $db = mysqli_connect("127.0.0.1","root","密碼","數據庫名")or die("Mysql連接失敗".mysqli_connect_error());
        $db = new mysqli("127.0.0.1","root","密碼","數據庫名",3306);
//        $data = $db->query("select * from ecs_users where user_id = 1 for update")->fetch_assoc();
        $data = mysqli_query($db,"select * from ecs_users where user_id = 1 for update")->fetch_assoc();
        var_dump($data);die;
    }