backup question

I've recompiled php 4.2.2 with curl support for a friend (on a redhat 8.0 machine). Before I do the 'make install', I want to back up his existing php libraries & such, so that if the newly compiled version doesn't work, i can revert to the old version. Can anyone tell me what I need to back up? Is it just the apache module (/etc/httpd/modules/libphp4.so)? Something tells me there's more to it than this. thanks. -rob