Mengakses output prosedur tersimpan MySQL di Zend Framework 2

ini pasti berhasil, karena saya sedang menggunakannya :

    $str = "DECLARE @Msgvar   varchar(100);DECLARE @last_id int;

    exec CallEntry_Ins $CallLoginId,".$this->usrId .",@Msg = @Msgvar OUTPUT,@LAST_ID = @last_id OUTPUT;

    SELECT  @Msgvar AS N'@Msg',@last_id AS '@LAST_ID'; ";


    $stmt = $db->prepare($str);
    $stmt->execute();
    $rtStatus = $stmt->fetchAll();



     $rtStatus[0]["@LAST_ID"] //accessing Op para