PDO FETCH OBJ Return False

Hello,

I did a update of my php server version and now one of my PDO query doesn't work anymore (it was working for more than a year).
It return Boleen false.
I'm connected to a Mssql server.
My connection is correct because all other queries work fine.
My SQL query work fine into Ms sql management studio console.

Someone can tell me what's wrong.
Here my query:

<?
$db = new UseDB(UseDB::MyDB);

$SQL = "DECLARE @vWL_NUMBER varchar(10);
exec @vWL_NUMBER = uspGetNextControlCode 'WL_NUMBER';
select @vWL_NUMBER as WL_NUMBER ";
$q = $db->query($SQL);

$row = $q->fetch(PDO::FETCH_OBJ);
$WL_NUM=$row->WL_NUMBER;

?>