Undefined variable: s_id

[wxdqz]

output:
Warning: Undefined variable: s_id in C:\Inetpub\wwwroot\Rose\it\screen2.php on line 18

source code:
<?php
if ($submit == "submit"){
$connection = mysql_connect ("", "", "");
if ($connection == false){
echo mysql_errno().": ".mysql_error()."<BR>";
exit;
}
$id = uniqid("s_id");
$query = ("insert into job (s_id, subject, assignTo, dateAss, progName, cFiles, newFile, fieldName, progFlow, cMenu, menuName, optDesc, revStatus, replySol, updateDoc)
values ('$s_id','$subject', '$assignTo', '$dateAss', '$progName', '$cFiles', '$newFile', '$fieldName', '$progFlow', '$cMenu', '$menuName', '$optDesc', '$revStatus', '$replySol', '$updateDoc')");
mysql_select_db("login",$connection);
$result = mysql_query($query,$connection);

the problem is: what's wrong with my source code when then output appear Undefined variable: s_id ...?? pls assist..
tq..

-maiza-