mysql_query("delete from online where time<".(time()-15*60)) or die(mysql_error());
$query=mysql_query("select * from online where ip='".db_input($_SERVER['REMOTE_ADDR'])."' and UserAgent='".db_input($_SERVER['HTTP_USER_AGENT'])."'") or die (mysql_error());
if(mysql_num_rows($query)==0)
{
mysql_query("insert into online values('".$_SERVER['REMOTE_ADDR']."','".$_SERVER['HTTP_USER_AGENT']."',".time().",'".$_GET['p']."')") or die('Cannot insert into MySQL '.mysql_error());
}else mysql_query("update online set time=".time()." where ip='".db_input($_SERVER['REMOTE_ADDR'])."' and UserAgent='".db_input($_SERVER['HTTP_USER_AGENT'])."'") or die(mysql_error());
$query=mysql_query("select * from online");
return mysql_num_rows($query);
}