Concurrent Apache modules and versioning

I would like to run both PHP 3 and PHP 4 as concurrent Apache modules. To work around problems with FreeTDS support with PHP 4.0.x, I've built PHP 3.0.16 with versioning support. Specific problems fixed by downgrading include regular core dumps and "Document contained no data" errors. Plastform is SunOS 5.8 x86 and FreeTDS 0.50 and recent snapshots. I need PDF support in PHP, and I would prefer to have it in the same version of PHP as is serving out the pages. But it is almost impossible to find PDFLib 2.x anymore. If anybody knows of a location, i'd be happy to try it. In the meantime, I've built PHP 3.0.16 with FreeTDS's Sybase-CT support and nothing else, and i've built PHP 4.0.1pl2 (and some recent snapshots) with jpeg, gif, png, tiff, zlib, and pdflib support. My question is: can I include() a PHP4 document and have the versioning figure out that I want the functions from the PHP4 module? Or would I need to POST the contents of a PHP 3 document to a PHP 4 document, loaded with the correct variables, and have it generate the PDF? Thanks.. Steven Campbell