else if ($login === true)
        {
            include 'include/aside.php';
            include 'include/footer.php';
            $id = id_from_username($username);
            $_SESSION['id'] = $id;
            redirect('index.php','2'); // a replacement for header()
            echo 'Login Success.';
            exit();
        }

if(isset($_SESSION['id']))
{
    return true;
}
else
{
    return false;
}

function login($username, $password) {
$username = mysql_real_escape_string($username);
$password = md5($password);
$loginquery = mysql_query("SELECT id FROM `users` WHERE `username` = '$username' AND `password` = '$password' LIMIT 1");
return (mysql_num_rows($loginquery) == 1);}