public function actionLoginWithModel()
 {
     $error = null;
     $model = new \app\models\LoginForm();
     if ($model->load(Yii::$app->request->post())) {
         if ($model->validate() && $model->user != null) {
             Yii::$app->user->login($model->user);
         } else {
             $error = 'Username/Password error';
         }
     }
     return $this->render('login-with-model', ['model' => $model, 'error' => $error]);
 }