Response Time

[Mythotical]

I am trying to get this to properly give the average response time for tickets. Similar to what is on vb.com but for the life of me it won't work. Gives me -34613 hours and -14 mins, very annoying.

Here is the function:

PHP Code:

function getResponseTime()
{
  global $db, $vbulletin, $hour, $minute;
  $result = $db->query_read("SELECT * FROM `" . TABLE_PREFIX . "pl9_support_tickets` ORDER BY tid DESC LIMIT 30");
  $ticket_num = $db->num_rows($result);
  if($ticket_num > 0)
  {
     $i = 0;
     $seconds = 0;
     while ($res = $db->fetch_array($result)){
            $query = $db->query_first("SELECT radded FROM `" . TABLE_PREFIX . "pl9_support_replies` WHERE ticket='". $res['tid'] ."' ORDER BY radded ASC LIMIT 1");
            $query_num = $db->num_rows($query);
            $rep = strtotime($query['radded']);
            $tick = strtotime($res['tadded']);
            $seconds += ($rep - $tick);
            $i++;
     }
     if($i>0)
     {
        $avg = $seconds / $i;
     }
  } else {
     $avg = 0;
  }
  $hour = round($avg/3600);
  $resttime = $avg - ($hour*3600);
  $minute = round($resttime/60);
  return;
} 


The way I use it in my script is adding this line:

PHP Code:

$response_time = getResponseTime(); 


Then in my template I have:

$hour:$minute

Am I trying to do this wrong? Could someone please provide a proper function that will do this right?

Thanks
Steve