date("Y-m-d H:i:s")
$GLOBAL_user['users_lastactive']

CREATE TABLE IF NOT EXISTS `users` (
  `users_id` int(11) NOT NULL AUTO_INCREMENT,
  `users_range` int(11) NOT NULL,
  `users_nickname` varchar(25) NOT NULL,
  `users_email` varchar(100) NOT NULL,
  `users_password` varchar(32) NOT NULL,
  `users_salt` varchar(5) NOT NULL,
  `users_activate` varchar(32) NOT NULL,
  `users_ipreg` varchar(100) NOT NULL,
  `users_iplast` varchar(100) NOT NULL,
  `users_lastvisit` datetime NOT NULL,
  `users_lastactive` datetime NOT NULL,
  PRIMARY KEY (`users_id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 AUTO_INCREMENT=6 ;

UPDATE `users` 
    SET users_lastvisit = IF(users_lastactive + INTERVAL 30 MINUTE < NOW(),NOW(),users_lastvisit),
        users_lastactive = NOW()
   WHERE `users_email`='$users_email'