The current number of online users on the website

This is the online statistics part of my multi-user statistics

gb_temp table:
temp1 User ID
temp2 browse IP address
temp3 online//A mark is made, because other functions also need to use this table
temp4 login time

$onlinetimeMaximum offline time minutes
db_class is a database operation class I define.

///////////////////
//Online statistics
$db = new db_class;
$db->connect();

$limit_time = time() - ($onlinetime * 60);
$online_time = time();

$db->query("delete from gb_temp where (temp4<$limit_time or temp2='$ip') and temp1='$id' and temp3='online'"); //Delete users offline for $onlinetime minutes
$db->query("insert into gb_temp (temp1,temp2,temp3,temp4) values ('$id','$ip','online','$online_time')");
$onres = $db->query("select count(*) from gb_temp where temp1='$id' and temp3='online'");
$onlineuser = $db->fetch_array($onres);
$onlineuser = $onlineuser[0];