//Important to remove all the old session entries for users who are not currently connected to the site
$sql = "UPDATE `userdata` SET `session_id` = '' WHERE `last_visit` <= '".date("Y-m-d H:i:s", mktime(date("H"), date("i")-30, date("s"), date("n"), date("j"), date("Y")))."' ";
mysql_query($sql);
$sql = "SELECT * FROM `userdata` WHERE `user_id` = '$_SESSION[user_id]' ";
$result = mysql_query($sql);
$row = mysql_fetch_assoc($result);
?>