title: Yii2 app\controllers\response not found using yii2-widget-depdrop extension
body: <p>I am new to yii2 and php web app development. I am using dep-drop  for selecting input
  depending on parent selection. Now I get an error message in yii2 debugger,</p>
  
  <pre><code>exception 'yii\base\ErrorException' with message 'Class 'app\controllers\Response' not found' in G:\xampp\htdocs\project\controllers\SalesOrderController.php:129 Stack trace: #0 [internal function]: yii\base\ErrorHandler-&gt;handleFatalError() #1 {main}
  </code></pre>