[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_User.php

<?php
final class SERIAL_User
{
        public $username = '';
        public $password = '';        public $userlevel = 0;
        
        public function __construct($username, $password, $userlevel=0)
        {
                $this->username = $username;                $this->password = $password;
                $this->userlevel = $userlevel;
        }
        
        public function getUsername()        {
                return $this->username;
        }
 
        public function getPassword()        {
                return $this->password;
        }
 
        public function getUserlevel()        {
                return $this->userlevel;
        }
}
?>