PHP extensions and multiple source files?

Howdy folks! Is there a way to have multiple *.c source files and still end up with a single *.so while using gcc? How would that be reflected in the config.m4 file? I searched for examples in the source tree, but did not find one. I tried different things, but ended up with multiple *.so's. I have been using *.h for a few pieces, but compiling gets long and the source a bit unwieldy. Thanks!