Session Problem

<?php

/* setup includes */
require_once('includes/master.inc.php');  

$Auth->logout();
redirect(WEB_ROOT);

<?php

// Application flag
define('SPF', true);  

// Determine our absolute document root
define('DOC_ROOT', realpath(dirname(__FILE__) . '/../'));  

// Global include files
require DOC_ROOT . '/includes/functions.inc.php'; // __autoload() is contained in this file  
require DOC_ROOT . '/includes/class.dbobject.php';  
require DOC_ROOT . '/includes/class.objects.php';  
require DOC_ROOT . '/includes/email_class/class.phpmailer.php';  
require DOC_ROOT . '/includes/phpqrcode/phpqrcode.php';  
require DOC_ROOT . '/includes/recaptcha/recaptchalib.php';  

// Fix magic quotes
if (get_magic_quotes_gpc())
{
    $_POST    = fix_slashes($_POST);
    $_GET     = fix_slashes($_GET);
    $_REQUEST = fix_slashes($_REQUEST);
    $_COOKIE  = fix_slashes($_COOKIE);
}

// Load our config settings
$Config = Config::getConfig();

/* load db config settings into constants */
$db   = Database::getDatabase();
$rows = $db->getRows("SELECT config_key, config_value FROM site_config ORDER BY config_group, config_key");  
if (COUNT($rows))
{
    foreach ($rows AS $row)
    {
        $constantName = "SITE_CONFIG_" . strtoupper($row['config_key']);  
        define($constantName, $row['config_value']);  
    }
}

// store session info in the database?
if ($Config->useDBSessions === true)
{
    DBSession::register();
}

// Initialize our session
session_name($Config->sessionName);
session_start();

// pick up any requests to change the site language
if (isset($_REQUEST['_t']))  
{
    // make sure the one passed is an active language
    $isValidLanguage = $db->getRow("SELECT languageName, flag FROM language WHERE isActive = 1 AND languageName = '" . $db->escape(trim($_REQUEST['_t'])) . "' LIMIT 1");  
    if ($isValidLanguage)
    {
        $_SESSION['_t'] = trim($_REQUEST['_t']);  
    }
    else
    {
        $_SESSION['_t'] = SITE_CONFIG_SITE_LANGUAGE;  
    }
}
elseif (!isset($_SESSION['_t']))  
{
    $_SESSION['_t'] = SITE_CONFIG_SITE_LANGUAGE;  
}

/* setup translations */
translate::setUpTranslationConstants();

// Initialize current user
$Auth = Auth::getAuth();

// Object for tracking and displaying error messages
$Error = Error::getError();

define("SITE_IMAGE_PATH", WEB_ROOT . "/themes/" . SITE_CONFIG_SITE_THEME . "/images");  
define("SITE_CSS_PATH", WEB_ROOT . "/themes/" . SITE_CONFIG_SITE_THEME . "/styles");  
define("SITE_JS_PATH", WEB_ROOT . "/themes/" . SITE_CONFIG_SITE_THEME . "/js");  

// the root plugin directory
define('PLUGIN_DIRECTORY_NAME', 'plugins');  
define('PLUGIN_DIRECTORY_ROOT', DOC_ROOT . '/' . PLUGIN_DIRECTORY_NAME . '/');  
define('PLUGIN_WEB_ROOT', WEB_ROOT . '/' . PLUGIN_DIRECTORY_NAME);  

// admin paths
define('ADMIN_WEB_ROOT', WEB_ROOT . '/admin');  

/* check for banned ip */
$bannedIP = bannedIP::getBannedType();
if (strtolower($bannedIP) == "whole site")  
{
    header('HTTP/1.1 404 Not Found');  
    die();
}

// setup demo mode
if (_CONFIG_DEMO_MODE == true)
{
    if (isset($_REQUEST['_p']))  
    {
        $_SESSION['_plugins'] = false;  
        if ((int) $_REQUEST['_p'] == 1)  
        {
            $_SESSION['_plugins'] = true;  
        }
        unset($_SESSION['pluginConfigs']);  
    }

    if (!isset($_SESSION['_plugins']))  
    {
        $_SESSION['_plugins'] = true;  
        unset($_SESSION['pluginConfigs']);  
    }
}

// load plugin configuration into the session
if (!isset($_SESSION['pluginConfigs']))  
{
    $_SESSION['pluginConfigs'] = pluginHelper::loadPluginConfigurationFiles();  
}

// append any plugin includes
pluginHelper::includeAppends('master.inc.php');  

    public function login($un, $pw)
    {
        $pw = $this->createHashedPassword($pw);
        return $this->attemptLogin($un, $pw);
    }

    public function logout()
    {
        $Config = Config::getConfig();

        $this->id = null;
        $this->username = null;
        $this->level = 'guest';  
        $this->user = null;
        $this->loggedIn = false;

        if (class_exists('User') && (is_subclass_of('User', 'DBObject')))  
            $this->user = new User();

        $_SESSION['un'] = '';  
        $_SESSION['pw'] = '';  
        unset($_SESSION['un']);  
        unset($_SESSION['pw']);  

        setcookie('spf', '.', time() - 3600, '/', $Config->authDomain);  
    }