Change :

Code:
  if ( isset( $_SESSION['REDIRECT'] ) && $_SESSION['REDIRECT'] != "" )
            {
                $redirect_url = $_SESSION['REDIRECT'];
                $_SESSION['REDIRECT'] = "";
            }
            else
            {
                $redirect_url = $config['baseurl']."/".$user_info['username'];
            }
            redirect( $redirect_url );
to:

Code:
 
$next = $_GET['next'];
if ($next == ""){
 if ( isset( $_SESSION['REDIRECT'] ) && $_SESSION['REDIRECT'] != "" )
            {
                $redirect_url = $_SESSION['REDIRECT'];
                $_SESSION['REDIRECT'] = "";
            }
            else
            {
                $redirect_url = $config['baseurl']."/".$user_info['username'];
            }
            redirect( $redirect_url );
}else{
                
            redirect( $next );
}
Now just make links like this:

http://site.com/login?{$baseurl}/whatever