OOP和AJAX表单提交问题

通过ajax提交我的表单后，消息总是返回失败，即使有正确的登录信息!我已经编码了这在一个非面向对象的风格，它的工作完美，但当我使用这种风格的代码挂起。活动站点为http://andyholmes.me/demo/summersproperty/OOP/login.php，用户名为admin@summersproperty.com，密码为admin

login -

    <?PHP
session_start();
include('includes/class.login.php');
$login = new Login();

$token = $_SESSION['token'] = md5(uniqid(mt_rand(), true));
if ($_POST['ajax']) {
    exit($login->getStatus());
}
?>
<style>
    #message { display: none; cursor: pointer; }
    .loader { display: none; }
</style>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/2.0.0/jquery.min.js"></script>
<script>
$(document).ready(function(){
    $("#loginForm").submit(function(e) {
        $(this).fadeOut(300);
        $('.loader').delay(300).fadeIn(100);
        $.post("<?=$_SERVER['PHP_SELF'];?>", { username: $('#username').val(), password: $('#password').val(), ajax: true }).done(function(data) {
            if (data.logged_in == true) {
                // Redirect with javascript
                $('.loader').delay(2000).fadeOut(100);
                $('#message').html('<p>Success! We''ll redirect you in a minute...</p>').delay(2200).fadeIn(200);
            } else {
                $('.loader').delay(2000).fadeOut(100);
                $('#message').html('<p>Failed... Click to try again!').delay(2200).fadeIn(200);
                $('#message').on('click', function(){
                    $(this).fadeOut(200);
                    $('#loginForm').delay(350).fadeIn(200);
                });
            }
        }); 
        return false;
    });
});
</script>
<form id="loginForm" method="POST" action="">
    <table>
        <tr><td>Username:</td><td><input type="text" name="username" id="username"/></td></tr>
        <tr><td>Password:</td><td><input type="password" name="password" id="password"/></td></tr>
    </table>
    <input type="hidden" name="token" value="<?=$token;?>"/>
    <input type="submit" name="login" value="Log In"/>
</form>
<div class="loader">
    <img src="loader.gif"/>
</div>
<div id="message"></div>

和登录类-

<?PHP
class Login 
{
    private $_id;
    private $_username;
    private $_password;
    private $_passmd5;
    private $_errors;
    private $_access;
    private $_login;
    private $_token;
    public function __construct()
    {
        $this->_errors = array();
        $this->_login  = isset($_POST['login']) ? 1 : 0;
        $this->_access = 0;
        $this->_token  = $_POST['token'];
        $this->_id     = 0;
        $this->_username = ($this->_login) ? $this->filter($_POST['username']) : $_SESSION['username'];
        $this->_password = ($this->_login) ? $this->filter($_POST['password']) : '';
        $this->_passmd5  = ($this->_login) ? md5($this->_password) : $_SESSION['password'];
    }
    public function isLoggedIn()
    {
        ($this->_login) ? $this->verifyPost() : $this->verifySession();
        return $this->_access;
    }
    public function filter($var)
    {
        return preg_replace('/[^a-zA-Z0-9]/','',$var);
    }
    public function verifyPost()
    {
        try
        {
            if(!$this->isTokenValid())
                throw new Exception('Invalid form submission');
            if(!$this->isDataValid())
                throw new Exception('Invalid form data entered');
            if(!$this->verifyDatabase())
                throw new Exception('Invalid username/password combination');
        $this->_access = 1;
        $this->registerSession();
        }
        catch(Exception $e)
        {
            $this->_errors[] = $e->getMessage();
        }
    }
    public function verifySession()
    {
        if($this->sessionExist() && $this->verifyDatabase())
            $this->_access = 1;
    }
    public function verifyDatabase()
    {
        include('dbConfig.php');
        $data = mysql_query("SELECT user_id FROM users WHERE user_username = '{$this->_username}' AND user_password = '{$this->_passmd5}'");
        if(mysql_num_rows($data))
        {
            list($this->_id) = @array_values(mysql_fetch_assoc($data));
            return true;
        }
        else 
        {
            return false;
        }
    }
    public function isDataValid()
    {
        return (preg_match('/^[a-zA-Z0-9]/', $this->_username) && preg_match('/^[a-zA-Z0-9]/', $this->_password)) ? 1 : 0;
    }
    public function isTokenValid()
    {
        return (!isset($_SESSION['token']) || $this->_token != $_SESSION['token']) ? 0 : 1;
    }
    public function registerSession()
    {
        $_SESSION['id'] = $this->_id;
        $_SESSION['username'] = $this->_username;
        $_SESSION['password'] = $this->_passmd5;
    }
    public function sessionExist()
    {
        return (isset($_SESSION['username']) && isset($_SESSION['password'])) ? 1 : 0;
    }
    public function showErrors()
    {
        echo "<h3>Errors</h3>";
        foreach($this->_errors as $key=>$value)
            echo $value."<br>";
    }
    public function getStatus()
    {
    return json_encode(array('logged_in' => $this->isLoggedIn(), 'errors' => $this->showErrors()));
    }   
}
?>

顺便说一句，我知道我需要使用PDOs等，但我只是想让脚本到一个点，在我改变数据库连接数据之前，它很好地工作。我知道我已经接近了，但这真的很令人沮丧!

如果你能帮助我，我将非常感激!

编辑说明:这段代码已经更新，因为使用user1781670