title: Dropdown in yii2 Not working
body: <p>I'm trying to bring dropdown in my header. Dropdown label coming. But, dropdwon values not coming. What may be the problem ?</p>
  
  <pre><code>&lt;?php
  
  /* @var $this \yii\web\View */
  /* @var $content string */
  
  use yii\helpers\Html;
  use yii\bootstrap\Nav;
  use yii\bootstrap\NavBar;
  use yii\bootstrap\Dropdown;
  use yii\widgets\Breadcrumbs;
  use app\assets\AppAsset;
  
  AppAsset::register($this);
  ?&gt;
  
  &lt;div class="wrap"&gt;
  &lt;?php
      NavBar::begin([
      'brandLabel' =&gt; 'My Company',
      'brandUrl' =&gt; Yii::$app-&gt;homeUrl,
      'options' =&gt; [
          'class' =&gt; 'navbar-inverse navbar-fixed-top',
      ],
      ]);?&gt;
  
  &lt;?
      echo Nav::widget([
      'options' =&gt; ['class' =&gt; 'navbar-nav navbar-right'],
      'items' =&gt; [
          ['label' =&gt; 'Danish Enam', 'url' =&gt; ['/site/register']],
          ['label' =&gt; 'Dropdown', 'url' =&gt; ['#'],
           ['label' =&gt; 'DropdownA', 'url' =&gt; '/'],
               ['label' =&gt; 'DropdownB', 'url' =&gt; '#'],
          ],
      ],
      ]);
  NavBar::end();
  ?&gt;
  </code></pre>
  
  <p></p>
  
  <p>Here is screenshot. 
  You all can clearly see. Dropdown coming in header. Right to 'My Company' Text. But, no values are coming. Not clickable.
  <a href="https://i.stack.imgur.com/YVp70.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/YVp70.png" alt="enter image description here"></a></p>
  
  <p>Any Idea ?</p>
  
  <p><a href="https://i.stack.imgur.com/Dwohg.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Dwohg.png" alt="enter image description here"></a></p>