[WeChall] Are you serial

We are serialsly trying to build a secure website.
This time, we have it secure and extensible, and of course you can see all the sourcecode again:

code.php
insecure.inc.php
SERIAL_LoginForm.php
SERIAL_LogoutForm.php
SERIAL_Solution.php
SERIAL_User.php

As always, code you see is code in use.

GeSHi`ed PHP code for SERIAL_LogoutForm.php

<?php
final class SERIAL_LogoutForm
{
        public function serial_formz()
        {                $data = array();
                $data['logout'] = array(GWF_Form::SUBMIT, 'Logout');
                return new GWF_Form($this, $data);
        }
                public function execute()
        {
                unset($_COOKIE['serial_user']);
                
                setcookie('serial_user', '', 0, GWF_WEB_ROOT_NO_LANG, GWF_DOMAIN, false, true);        }
}
?>