How to do a minimal compile?

I'm trying to tweak performance out of a web serving machine, and therefore am trying to save every bit of RAM possible. I've gotten my Apache compiled down to only have the bare bones needed modules in it. Now I'm turning to PHP. But I'm having troubles seeing how to compile PHP without certain parts in it, to give it a smaller footprint. Things such as MySQL support. Heck, if possible, I'd even like to take out more entire 'extensions' that I know I won't be using ... But all I seem to see in the documentation is how to ADD extensions, not how to remove ones that are there, and you don't need. Eli