I am currently using various back-end services and I want to use PHP to simply query these services and perform the final page construction. These services could be coded in any number of programming langauges such as Erlang, Java, Python etc. However I am unsure of the best way to actually interface the back-end services with the web app. Requests to these services would be both synchronous and asynchronous. Would I use something like SOAP or JSON-RPC??
Any help greatly appreciated.