/**
  * Group materials
  */
 protected function groupMaterials()
 {
     if (!count((array) $_POST['item_ids'])) {
         ilUtil::sendFailure($this->lng->txt('select_one'), true);
         $this->ctrl->redirect($this, 'show');
     }
     // Assign new grouping id
     include_once './Services/Tracking/classes/class.ilLPCollections.php';
     ilLPCollections::createNewGrouping($this->getObjId(), (array) $_POST['item_ids']);
     // refresh learning progress
     include_once "./Services/Tracking/classes/class.ilLPStatusWrapper.php";
     ilLPStatusWrapper::_refreshStatus($this->getObjId());
     ilUtil::sendSuccess($this->lng->txt('trac_settings_saved'), true);
     $this->ctrl->redirect($this, 'show');
 }