Recompile PHP on pre-installed system

Before I came to my company, they created a Redhat server for our web server. Of course they let the redhat installer install PHP. It all works great but now I need to compile a module into php. Is this possible to do without causing havok? Bascially we really can't have more downtime that it would take to stop and start Apache. Would the best solution be to download the php source, compile it into the directory it is installed into now, but only compile with the new module or will I need to compile it using the --with-apxs and all of the other modules that it is already compiled with? I would rather not have to recompile with all of the options that it is compiled with now. Thanks for you help!