codeigniter-affiliates-program

<?php
  //check for referal links
  function referal()
  {
   $CI =& get_instance();
   $cookie_value_set = $CI->input->cookie('_tm_ref', TRUE) ? $CI->input->cookie('_tm_ref', TRUE) : '';
  if ($CI->input->get('ref', TRUE) AND $cookie_value_set == '') {
    // referred user so set cookie to ref=username
     $cookie = array(
    'name'   => 'ref',
    'value'  => $CI->input->get('ref', TRUE),
    'expire' => '7776000',
  );
    $CI->input->set_cookie($cookie);
    return TRUE;
   }elseif ($cookie_value_set == '') {
     $cookie = array(
    'name'   => 'ref',
    'value'  => 'sso',
    'expire' => '15552000',
  );
    $CI->input->set_cookie($cookie);
    return TRUE;

   }elseif ($cookie_value_set != '') {
     //already referred so ignore
    return TRUE;

   }else{
      return TRUE;
   }
  }
  //end of hooks file

@wmandai, why use webhook? and for referral system.. which one between using cookies or session are better option?
I assume ref link as website.com/r/uid, how to accomplish this? Any guide for me?