Here is my situation, please bear with me. I am running
Zen Cart 1.2.4.1
Database Patch Level: 1.2.2

I would like to integrate some code written in PHP5 into Zencart. The code is fairly extensive and it wouldn't make sense to rewrite it to support PHP4. It makes heavy use of the newfangled SOAP implementation that doesn't support PHP 4. Using another library, such as NuSoap or Pear is too different.

We already made extensive changes to the templates and after reviewing the new Zencart release, it would be quite a feat to convert them to the lastest version. It would also mean we would have to retest the entire system and make sure nothing is broken. Upgrading Zencart isn't a viable option.

One solution is to run the current version of zencart under PHP5 and it is known to have problems with PHP5. After typing in the login info, it sends me back to the same page with no error. Checkout drops the entire shopping cart after attempting to login. The rest of the site, however, seems to work fine. I believe the problem is related to sessions.

If I can manage to solve this one hurdle I am homefree and I can start integrating the PHP5 code into Zencart. Any help out there?