Menampilkan status OFFLINE/ONLINE user

[toplirik]

Mbah Dokter  Gw buat web member sistem dimana tiap user yang login, maka secara otomatis akan tercatat/log di database field status = ON, dan jika logout maka otomatis berubah status = OFF.

Di forum ini terdapat status user ONLINE/OFFLINE, nah itu logikanya spt apa ya dok? berdasarkan $_SESSION atau bgmn? Apa perlu dengan relasi? tlng dikasih pencerahan 

Contoh database dan scriptnya spt ini :

Code:

#### DATABASE LOG STATUS ####
CREATE TABLE `plus_login` (
  `id` varchar(50) NOT NULL default '',
  `userid` varchar(10) NOT NULL default '',
  `status` char(3) NOT NULL default 'ON'
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

INSERT INTO `plus_login` VALUES ('1d20d7b8ae1e917692516955ff210d70', 'sugix', 'OFF');



#### MEMBER ####
CREATE TABLE `member` (
  `uid` int(10) NOT NULL auto_increment,
  `userid` varchar(10) NOT NULL default '',
  `password` varchar(32) NOT NULL default '',
  `email` varchar(50) NOT NULL default '',
  PRIMARY KEY  (`uid`),
  UNIQUE KEY `email` (`email`),
  UNIQUE KEY `uid` (`uid`),
  UNIQUE KEY `userid` (`userid`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=12 ;


INSERT INTO `data_alumni` VALUES (1, 'sugix', 'sugix', 'sugix@indodesign.net');


### tampil_member.php ####

echo "
<table width=100% border=0 cellpadding=2 cellspacing=1>
<tr bgcolor=#AEC7E1>
<td><b>id</b></td>
<td><b>Username</b></td>
<td><b>Password</b></td>
<td><b>E-mail</b></td>
</tr>
";

$sql = "select * from member";
$exec = mysql_query($sql) or die(mysql_error());


while($mfa = mysql_fetch_array($exec)){

echo "
<tr>
<td><b>$mfa[uid]</b></td>
<td><b>$mfa[userid]</b></td>
<td><b>$mfa[password]</b></td>
<td><b>$mfa[email]</b></td>
<td><b>[b]XXXXX Disini mau diletakin statusnya apakah member tsb ONLINE/OFFLINE? XXXXXX[/b]</b></td>
</tr>
";

}
</table>

[webmaster]

itu sudah benar, cuma tambahin autentifikasi session pada query table

Code:

$qry = mysql_query("SELECT * FROM user_online WHERE username = '".$_SESSION['username']."' AND status='online'");