title: ZendFramework - How to create optgroup and there option using view helpers?
body: <p>How do i create this with $this->formSelect() ?</p>
  
  <pre><code>&lt;select multiple&gt;
      &lt;optgroup label="a"&gt;
         &lt;option&gt;1&lt;/option&gt; 
         &lt;option&gt;2&lt;/option&gt;
      &lt;/optgroup&gt;
      &lt;optgroup label="b"&gt;
         &lt;option&gt;1&lt;/option&gt; 
      &lt;/optgroup&gt;
  &lt;/select&gt;
  </code></pre>