Site in Multiple Languages

[iPodGratis]

Hi, I run an incentive site called www.iPodGratis.com. The script I'm running is called Project-Rafs. The script was originally in English but I've translated it into Spanish as this site is aimed at residents of Spain.
But due to high demand I am looking to start the site in the UK too, therefore the site also needs to be in English, but still be available in Spanish.
A similar site to mine called www.euroipods.com is doing it and somehow keeping their original URL.

For example:
English referral page is www.euroipods.com/referfriends.php
Spanish referral page is www.euroipods.com/referfriends.php

Also the member’s referral link is the same no matter what language it’s in, it’s always http://www.euroipods.com/index.php?referral=XX

They are not using a free translator or anything similar as the translations are too good, not only that, but even the images change from English to Spanish, yet keeping the same URL.

Please let me know if you have any ideas, it's greatly appreciated.

Yours Sincerely,
Lee.

[ealex]

well as far as I can see it's all done in php.
there's differents versions of the same site in different languages, but all the data is stored in databases and loaded dynamically using php and javascript to set the cookie language variable.