public function checkLogin(){

        if (isset($_GET['page']) && ($_GET['page'] == 'signup'))
        {
            return false;   //prevents the 'incorrect username/pw' message from being displayed, since both use the same 'post' variable names
        }
        else if ( isset($_POST['username']) && isset($_POST['password']))
        {
            if ( $_POST['username'] )
                $username = mysql_real_escape_string($_POST['username']);
            if ( $_POST['password'] )
                $password = mysql_real_escape_string($_POST['password']);

            $password = md5($password . 's4lt_141812');

            $q = "SELECT * FROM usertable WHERE user_name = '$username' AND user_password = '$password'";
            $r = mysql_query($q);

            if ( $r !== false && mysql_num_rows($r) > 0 )
            {
            //  echo '<p>Successfully logged in</p>';
                $_SESSION['username'] = $username;
            }
            else
                echo '<p>Incorrect username / password combination</p>';
        }
    }