title: yii2:drop-down list for multiple values concat in one line
body: <p>for my drop-down list I am using this code.</p>
  
  <pre><code>&lt;?= $form-&gt;field($medicinerequest, '[' . $id . ']' . 'medicine_name')
  -&gt;DropDownList(ArrayHelper::map(\app\models\Medicine::find()
  -&gt;asArray()-&gt;all(), 'id', 'medicine_name','medicine_id' ),
  [ 'prompt' =&gt; 'Please Select' ])?&gt; 
  </code></pre>
  
  <p>I am getting the drop-down list as in the picture. But I want it to be concatenated by hyphen(-) in one line. How can I do this?</p>
  
  <p><img src="https://i.stack.imgur.com/y7mgM.jpg" alt="medicine-request-drop-down"></p>