Turn PHP Built in Web Server into a Proxy

PHPMonkey? I wanted to use PHP to alter web pages and http traffic, so I downloaded many scripts that said they were PHP proxy. I didn't find any that really worked, they all just fetched the page, mangled all the links, and puked it back at me. I couldn't log in to any website, and if the site I was visiting used javascript to inject links, scripts, and all sorts of other dynamic content these so called proxies failed horribly. So, I figured I'd try writing one myself, and I've come up with something that works.