What we are looking here is a client-server architecture with multiple players (clients) simultaneously connected to the central game-server. So, what are the recomendations for the server-side language and the client-side languague. Thanks alot !
Well, you have a lot of options, I would use php on the server side, and code it like a REST or RPC type interface, and just use javascript/jquery/ajax on the client side. No plugins needed, and will work in most browsers including smartphone browser. It is important to keep all the logic on the server side to prevent cheating, and just have the client relay user input. This is my recommendation, but I have seen many sites that use flash or java. All three methods have there pros and cons. I prefer php for it's simplicity and easy of use.
I would use PHP or ASP on server side language and Java Script or Ajax on client side scripting langauage as the casino games need more security from client side.