Integrating PHP & Python through a light-weight rpc mechanism?

[Iwan van der Kleyn]

Hi there,
At my company we've build a web-based cms/e-commerce framework over the 
years which is quite succesfull from a commercial perspective. It is 
complelely implemented in PHP and, though very fast, its internals are 
totally obfuscated and it has become nearly impossible to maintain. 
Replacing it is just too expensive, so the option we are considering is 
  to gradually trim back PHP to the presentational tier and to start 
using another language/platform for the middle/data tiers. Java then 
seems to be the obvious choice. However, considering productiveity 
levels I can reach with Python compared to Java, the average skill-set 
among the developers and just plain stubborness :-) I'm reviewing the 
possibility to  have Python as the target platform for the back-end.

But then, how do presentational and back-end tiers communicate? RPC 
mechanisms like Corba come to mind. But that seems to be very "heavy 
weight" and using Corba in Python/PHP is a rather involved affair. XML 
based mechanisms (SOAP, XML-RPC, ReST) are more easy but offer their own 
set of challenges (not the least the overhead of XML). You would expect 
that there would be some light-weight RPC protocol available, with the 
simplicity of XML-RPC and the compactness of a binary protocol. But I 
haven't found a suitable ptotocol. Is there any to be found which can be 
used from Python and PHP?

Regards,

Iwan