title: Yii2 Gridview Adding another Header
body: <p>I am using gridview to list all my data. my table looks like this.</p>
  
  <pre><code>&lt;?= GridView::widget([
      'dataProvider' =&gt; $dataProvider,  
      'columns' =&gt; [
          'firstName',
          'lastName',
          'startDate',
          'hiredDate'
      ],
  ]) ?&gt;
  </code></pre>
  
  <p>which renders a table like this.</p>
  
  <p><a href="https://i.stack.imgur.com/IqzEK.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/IqzEK.png" alt="enter image description here"></a></p>
  
  <p>how can i add another header for grouping NAME and DATE so that it will look like this. like rowspan in pure HTML.</p>
  
  <p><a href="https://i.stack.imgur.com/RQAly.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RQAly.png" alt="enter image description here"></a></p>