Regular expression validation is working clientside but not serverside

I have an Userid with the following syntax: It starts with the uppercase letters SSF followed by \ and a lowercase letter c. Then it's 3 numbers and 3 letters. (Example: SSF\c890rbr). I believe the regular expression for this should be /^SSF\\c\d{3}[a-zA-Z]{3}$/

The validation is working clientside but not serverside. The problem with the serverside validation is that a valid userid does not pass through.

You can test it on live URL here
Serverside: Serverside.php
Clientside: Clientside.php

I'm attaching my working files. I would very much like the serverside validation to work.

Thanks in advice.

Regards
Rune

the server side regular expression should be:
/^SSF\\\\c\d{3}[a-zA-Z]{3}$/


in PHP you need to use four slashes to escape the one:
\\\\

in javasctipt, you can use just the 2:
\\

Works perfect.

Thanks again.

Regards
Rune

you're welcome.