/**
  * 首页
  * @return string
  */
 public function actionIndex()
 {
     //首页获取collections,以备后面要用
     $session = Yii::$app->session;
     //$session->removeAll();
     $user = $session->get('user');
     $collections = Collection::findAllByUser($user['userId']);
     //以testLibraryId为索引,方便以后查key是否存在
     $collections = ArrayHelper::index($collections, 'testLibraryId');
     $session->set('collections', $collections);
     return $this->render('index');
 }