title: In Codeigniter, how to pass a third parameter to a callback (form validation)?
body: <p>I am currently using the Form Validation class (on Codeigniter) and setting rules.</p>
  
  <p>It works like this with two parameters (<a href="http://codeigniter.com/user_guide/libraries/form_validation.html" rel="noreferrer">codeigniter.com/user_guide/libraries/form_validation.html</a>):</p>
  
  <pre><code>$this-&gt;form_validation-&gt;set_rules('username', 'Username', 'callback_test[abc]');
  </code></pre>
  
  <p>But what about a third parameter? And a fourth...? Is it possible?</p>