calculating if a time is older than 10 minutes

[planetphp]

Hi,

I have a simple chat script that registers users that have posted a message within the last ten minutes. If they do not submit for longer than 10 minutes then they are removed from the online table.

The way i have done it at the moment is to select the minutes from a time field and compare it against the minutes of curtime.. but as you will be aware this doesnt always work. if the script is not refreshed within a certain time then the name is not deleted. resulting in a list of online users that aren't online...

I need a way of calling the time from the time field and comparing it against current time to see if its older than ten minutes...

heres my current code:

// deletes users from online table that havent posted in 10 minutes.

$online_query = "SELECT username, minute(lastpost), minute(curtime()) FROM online";
$online_result = mysql_query($online_query);
while($online_results = mysql_fetch_row($online_result))
{ 
    $user = $online_results[0];
    $time = $online_results[1];
    $cur_time = $online_results[2];

if($cur_time - $time >= 10 or $cur_time - $time < 0)
  {
    $result = mysql_query("delete from online where username='$user'");
  }
}

please help

[notionlogic]

Wouldn't it be better to do all this in the SQL query? It would certainly be quicker but perhaps your table isn't constructed in that way?