Sponsor id/email included in the link is not being utilized?

[chinfei]

                        $vars = array(
                           '{email}' => strval($cookie->email),
                           '{lastname}' => strval($cookie->customer_lastname),
                           '{firstname}' => strval($cookie->customer_firstname),
                           '{email_friend}' => $friendEmail,
                           '{lastname_friend}' => $friendLastName,
                           '{firstname_friend}' => $friendFirstName,
                           '{link}' => 'authentication.php?create_account=1&sponsor;='.urlencode($cipherTool->encrypt($referralprogram->id.'|'.$referralprogram->email.'|')),
                           '{discount}' => $discount);
                       Mail::Send((int)($cookie->id_lang), 'referralprogram-invitation', Mail::l('Referral Program'), $vars, $friendEmail, $friendFirstName.' '.$friendLastName, strval(Configuration::get('PS_SHOP_EMAIL')), strval(Configuration::get('PS_SHOP_NAME')), NULL, NULL, dirname(__FILE__).'/mails/');

Anyone has any clue whether the sponsor parameter is being used somewhere?
It's included in the link in the email send to sponsor friend of Referral Prorgam module.

I thought it should works like, when someone click on the link to register, it will auto fill up the sponsor email field or being utilized somewhere.
But it doesn't works that way in authentication.php or Referral Program module
except it's just being included in the link.