public static function getInstance()
 {
     if (!isset(self::$instance)) {
         $class = __CLASS__;
         self::$instance = new $class();
     }
     return self::$instance;
 }
 public function getFilterLogManager($browserId, $osId, $resolutionId)
 {
     $db = ncDatabaseManager::getInstance()->getDatabase('nLogger_heatmap')->getConnection();
     $dao = HeatmapFilterDAOFactory::getInstance()->getDAO($db, $browserId, $osId, $resolutionId);
     return new HeatmapFilterLogManager($dao);
 }