As is mentioned in this new post to DZone.com, one of the features of the upcoming PHP 5.4 release, including things like traits and array dereferencing support, will also have an interesting new feature - a built-in simple web server.
Yet another new feature to look forward to in PHP 5.4.0 - the CLI SAPI will now provide a built-in web server which is geared toward developmental purposes. It shouldn't be used in production right now.
The PHP manual has been updated with the latest on this upcoming feature:
URI requests are served from the current working directory where PHP was started, unless the -t option is used to specify an explicit document root. [...] If a PHP file is given on the command line when the web server is started it is treated as a "router" script for the web server. The script is run at the start of each HTTP request. If this script returns FALSE, then the requested resource is returned as-is. Otherwise the script's output is returned to the browser.