public function actionIndex()
 {
     $dataProvider = new CActiveDataProvider('Teachers', ['sort' => ['defaultOrder' => 'lastname ASC, firstname ASC, middlename ASC']]);
     $model = new Teachers('search');
     if (!Yii::app()->request->isAjaxRequest && !Yii::app()->request->getParam('ajax')) {
         $this->render('list', ['dataProvider' => $dataProvider, 'model' => $model]);
     } else {
         $model->setAttributes(Yii::app()->request->getParam('Teachers'));
         $dataProvider = $model->search();
         $dataProvider->setSort(['defaultOrder' => 'lastname ASC, firstname ASC, middlename ASC']);
         $this->renderPartial('_list', ['dataProvider' => $dataProvider, 'model' => $model]);
     }
 }