Problem with $_Get

[Manb]

hello,
in my complex layaout I want to creat a center region synchronized
with URL value.
this my code :
<?php
if(isset($_GET['erreur']) && $_GET['erreur'] == 'connecteA')
{
include 'GrigA.php';
$viewport->addItem($grid,
PhpExt_Layout_BorderLayoutData::createCenterRegion());

}
else{
include 'top.php';
$viewport->addItem($top,
PhpExt_Layout_BorderLayoutData::createCenterRegion());

}

?>
and when i click in my link I obtain in my URL bar this value :
http://localhost/V1/index.php?erreur=connecteA
but the center synchronization dont work.

please help me and thank you in advance .