private static function getPageGroupFromData($aoDataPageGroup)
 {
     $nPageGroupId = $aoDataPageGroup[0]->PageGroupId;
     $nPageGroupContentClass = $aoDataPageGroup[0]->PageGroupContentClass;
     $aoPages = array();
     foreach ($aoDataPageGroup as $oDataPage) {
         if ($oDataPage->PageId) {
             //warning : PageContent may be NULL when using performance+memory boost
             $oPage = self::getPageFromData($oDataPage);
             $sPageLang = $oPage->getLang();
             $aoPages[$sPageLang] = $oPage;
         }
     }
     $oPageGroup = AnwPageGroup::rebuildPageGroup($nPageGroupId, $nPageGroupContentClass, $aoPages);
     return $oPageGroup;
 }