Aide por ma requete svp

Bonjour,
Le principe est de récupérer une vairable via une url et de l'integrer dans ma requete seulement si elle se trouve dans l'url :

$region=$_GET['region'];
$query = "SELECT a.*, p.name as parent, p.id as parentid, c.name as cat, c.id as catid, $name as user
FROM #__adsmanager_ads as a
LEFT JOIN #__adsmanager_adcat as adcat ON adcat.adid = a.id
LEFT JOIN #__users as u ON a.userid = u.id
LEFT JOIN #__adsmanager_categories as c ON adcat.catid = c.id
LEFT JOIN #__adsmanager_categories as p ON c.parent = p.id
WHERE $search and c.published = 1";

if (isset($region)) {
$query.= "and a.ad_region ='$region'";
}
$query.="GROUP BY a.id ORDER BY $order_text";


Cela ne marche pas et je ne comprends pas
Merci pour toute suggestion
Cordialement