online users

im having some trouble getting this piece of code to work...
it is supposed to connect to the database and based on the last time a user did anything on the site it should tell me if they should be considered online or offline.

Right now the script shows everyone as being offline. I echoed the $online_time and get a result like "20080310104103" but on the mysql table the results are saved as "2008-03-10 10:41:03" is that the reason its not working?

$query = "select * from ".$prefix."access_log WHERE member_id = '$u_id' order by time DESC";
$result = MySQL_query($query); 
$rows = @mysql_fetch_array($result);
$access_time = $rows[time];
if ($access_time == ""){
$access_time = date("YmdHis");
}else{
$access_time = $rows[time] + 600;
}
$online_time = date("YmdHis") + 300;
if ($user_id == $login){
$edit = $l_profile_edit;
}
if ($access_time > $online_time){
$stat = "<font color=green>online</font>";
}else{
$stat = "<font color=red>offline</font>";
}

PHP: