title: Codeigniter validate checkbox group
body: <p>I have this html code that I want to validate using the Codeigniter <code>Form_Validation</code> class :</p>
  
  <pre><code>&lt;form id="thread" method="POST"&gt;
      &lt;input type="checkbox" name="checkAllAuto" id="checkAll" onclick="CheckAll(this.id)" /&gt;&lt;?php echo __t($dir_lang,'request_select_all');?&gt; 
      &lt;br /&gt;
      &lt;?php foreach ($threads as $thread): ?&gt;
      &lt;input type="checkbox" class="threads" name="option[]" value="&lt;?php echo $thread['th_id']; ?&gt;" /&gt; &lt;?php echo $thread['th_title']; ?&gt; &lt;br&gt;
      &lt;?php endforeach; ?&gt;
      &lt;br /&gt;
      &lt;input type="checkbox" name="mom" /&gt; &lt;?php echo __t($dir_lang,'request_send');?&gt; 
      &lt;br /&gt;
      &lt;select name="cat"&gt;
          &lt;?php foreach ($cats as $cat): ?&gt;
          &lt;option value="&lt;?php echo $cat['id']; ?&gt;"&gt; &lt;?php echo $cat['title']; ?&gt; &lt;/option&gt;
          &lt;?php endforeach; ?&gt;
      &lt;/select&gt;
      &lt;br /&gt;&lt;input type="submit" value="&lt;?php echo __t($dir_lang,'submit');?&gt; " /&gt;&lt;br&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>I'm trying to validate the fist group of the check box by using <code>Form_Validation</code></p>
  
  <pre><code>if ($this-&gt;input-&gt;isMethodPost())
  {
      $this-&gt;tplData['showMess'] = true;
      $this-&gt;load-&gt;library('form_validation');
      $this-&gt;lang-&gt;load('form_validation', 'english');
      $this-&gt;form_validation-&gt;set_error_delimiters('&lt;h3&gt;', '&lt;/h3&gt;');
      $this-&gt;form_validation-&gt;set_rules('options[]','options', 'required');
      if ($this-&gt;form_validation-&gt;run() == FALSE)
      {
          $this-&gt;tplData['showError'] = true;
          $this-&gt;tplData['mess'] = array(validation_errors());
      }else{ 
          // my work
      }
  }
  </code></pre>
  
  <p>It gives required filed message but even if I choose one or all the checkbox it still gives the required message.</p>