I have a web-based interface for handing invoices, customer records and other transaction records which interacts currently with a database of all the aforementioned stored upon the same machine. As you can imagine, this is quite a simple set-up consisting of a web-app (PHP) and a database (MySQL). However, the ideal scenario is to keep the records on the machine they are currently on (easy) and move the web-app to another server within the same network (again, easy) ... but in addition, provide facilities on a public-facing website for managing accounts by customers and so forth. The problem is this - the public-facing web server is located in a completely separate location as it is a dedicated server provided by a well-known ISP.
What would be the best way to enable the records to be accessible from this other server whilst ensuring that all communications are secure. Speed is not a huge factor, although any outages on either side should be handled gracefully. Initially my thoughts went towards web services (XML-RPC/SOAP/Hessian), but these options seem to present difficulties (security being the main one, overcomplexity as well).
The web-app must remain PHP-based. The public-facing site is likely to be PHP-based as well, although Python (likely using Django) is another option. The introduction of any other technologies (Java etc) is not a problem, although it is preferred if they be Linux-friendly (so .NET would not be the best fit here).
Apologies if this question is somewhat verbose and vague. I am testing the water somewhat in regards to this kind of problem. Any advice or suggestions gratefully received.