To keep track of the time a user logs in I created a field in the DB called LoginTime (Type : timestamp(10)). So when someone logs in, I use this :

PHP Code:
$sql = "UPDATE `users` SET `LoginTime`=NOW() WHERE `ID`=$id LIMIT 1 ;"; 
to set the time. Then, if I want to compare the time now with the time logged in, I get an error here :

PHP Code:
if ($row['LoginTime']+15 < NOW()){ 
So instead of NOW(), can I use time? Or maybe somehow format time to compare the two?

Thanks