Notice (8): Undefined index: HTTP_ACCEPT_LANGUAGE [APP/Controller/AppController.php, line 146]

        if (!$this->Session->check('Config.language')) {
            //checking the 1st favorite language of the user's browser
            $browserLanguage = substr($_SERVER['HTTP_ACCEPT_LANGUAGE'], 0, 2);

AppController::_checkBrowserLanguage() - APP/Controller/AppController.php, line 146
AppController::beforeFilter() - APP/Controller/AppController.php, line 77
ReservationsController::beforeFilter() - APP/Controller/ReservationsController.php, line 188
CakeEventManager::dispatch() - CORE/Cake/Event/CakeEventManager.php, line 244
Controller::startupProcess() - CORE/Cake/Controller/Controller.php, line 682
Dispatcher::_invoke() - CORE/Cake/Routing/Dispatcher.php, line 189
Dispatcher::dispatch() - CORE/Cake/Routing/Dispatcher.php, line 167
[main] - APP/webroot/index.php, line 109