title: Using multiple callbacks in form validation in codeigniter
body: <p>I am separating the logic of defining form validation rules into a library. i want to apply multiple callback functions on a single form element.</p>
  
  <pre><code>$this-&gt;form_validation-&gt;set_rules('email', 'email', 'callback_db_check|callback_valid_email');          
  </code></pre>
  
  <p>Now i don't know how to do this. Because its not working i mean multiple callback are not working. But if i define single callback its working fine.</p>
  
  <pre><code>function db_check(){
      $this-&gt;CI-&gt;form_validation-&gt;set_message('db_check', 'Not found in db');
  }
  
  function valid_email(){
      $this-&gt;CI-&gt;form_validation-&gt;set_message('db_check', 'Invalid email');
  }
  </code></pre>
  
  <p>This is just example code. I have extended form validation library so that i can define and call validation logic from my library . Any suggestion how i can do it?</p>