PHP/Zend Compiler

We are developing some specialized applications for which we do not wish to disclose our source code on. I understand there is a compiler in the works for Zend with the ability to compile to p-code and offer significant performance increase which also is appealing. I don't know how far along this project is, but I have a couple of questions and I am sorry if the have been asked before. Is there anything special to consider when programming php with the concept of compiling in the future? Can there be a mix of both compiled and none compiled code? Any time frame on when one might expect such a product to be available? Thanks, John Hamlik