counter virker ikke?

min counter virker ikke, den viser hele tiden 1 user online, også selvom der er flere + at den ikke gemmer ip adessen i min mySQL database, jeg har tager database oplysningerne væk fra scriptet:

<?php
global $REMOTE_ADDR, $display;

$data_refresh = 180;

$timestamp = time();
$user_ip = $REMOTE_ADDR;


$online_query = "SELECT * FROM {$db_table}";
$exists_query = "SELECT ip FROM {$db_table} WHERE ip='{$user_ip}'";
$update_query = "UPDATE {$db_table} SET timestamp='{$timestamp}' WHERE ip='{$user_ip}'";
$insert_query = "INSERT INTO {$db_table} (ip, timestamp) VALUES ('{$user_ip}', '{$timestamp}')";



$mysql_link = mysql_connect($db_host, $db_user, $db_pass);
mysql_select_db($db_name);


if (mysql_num_rows(mysql_query($exists_query)) == 0) {
mysql_query($insert_query);
} else {
mysql_query($update_query);
}

$online = mysql_query($online_query);
while($data=mysql_fetch_assoc($online)) {
$difference = $timestamp - $data['timestamp'];
if ($difference > $data_refresh) {

  $delete_query = "DELETE FROM {$db_table} WHERE timestamp='$data[timestamp]'";
  mysql_query($delete_query);
  $users_online = $users_online - 1;
}
}

$users_online = mysql_num_rows(mysql_query($online_query));

if ($users_online > 1) {
  print "$users_online users are online.";
} elseif ($users_online == "1") {
  print "$users_online user is online.";
} elseif ($users_online == "0") {
  print "There are no users online.";
}
?>

Håber en kan hjælpe takker