I have modified the _RegenerateId() method to this (according the phpmanual:
hu2.php.net/manual/en/function.sess ... ,
see this post: Nicolas dot Chachereau at Infomaniak dot ch, 02-Jun-2005 08:40)
The problem was that in php4 there isn't the optional parameter!
  function _RegenerateId()
  {
    if ($this->regenerate_id && function_exists('session_regenerate_id'))
    {
		$old_session_id = session_id();
		session_regenerate_id(); 
		$new_session_id = session_id();
		session_id($old_session_id);
		session_destroy();
		$old_session = $_SESSION;
		session_id($new_session_id);
		session_start();
		$_SESSION = $old_session;
    }
  }
Note from Nicolas dot Chachereau: "this technique will send 3 Set-Cookie headers (one on each session_start() and one on session_regenerate_id()). I don't think this is a problem, ..."
PS: and thanks for these great packages that You supplied, Vagharshak ! There're a lot of good idea ...