<?php
if(@$_SESSION['enter']=='yes')
{
$id=intval($_SESSION['uid']);
$timer=time();
if(!mysql_num_rows(mysql_query("SELECT * from `online` WHERE `id`='$id'")))
mysql_query("INSERT into `online` VALUES('$id','$timer')");
else
mysql_query("UPDATE `online` SET `time`='$timer' WHERE `id`='$id'");
}

?>