Add --enable-module=proxy to your Apache ./configure command.
refers to the compilation of httpd (the Apache web server program). If you already have it installed,
you've already completed the compilation (or you installed a compiled version).
It is possible that your installed Apache wasn't compiled with the given option, so what you're trying to do
may not work.
My advice, try configuring your apache first. If that doesn't work, you can consider recompiling Apache, with the given option.
But let me ask you this first: why would you need 2 Apache servers? Isn't one enough for you?
I believe any Apache can run PhP5, if it has the right module/config. But then again, I'm no expert either, so
I can be mistaken.