In a new post from Brian Moon looking at how they're (DealNews) using forking in PHP applications to handle some of their Gearman processing.

While at the OReilly Open Source Convention in 2009, we were asked about how we pulled this off. So, we are releasing the two scripts that handle the forking and some instructions on how we use them. [...] These are the scripts we use to manage long running processes. They work great for us on Linux. They will not run on Windows at all. We also never had any trouble running them on Mac OS X.

The two scripts (that you can grab on their developer site) show two methods for running child processes and how to pass off requests to each one to be handled in turn.