Jack Slingerland has a series of new posts to his blog looking at a method for multi-processing in PHP applications and some of the considerations of forking off processes from a main script.

Of all the glorious programming languages in existence, you've chosen to work with PHP. Okay, maybe you were forced to, but that doesn't mean you can't have fun right? Hmm, fun...What' fun? Threading, race conditions, and deadlocks. Sounds like loads of fun! But alas, PHP doesn't have functionality to cover this. True, but the host operating system does. We can just fork processes manually like in the good 'ole days' and then ride off into the sunset. But we shouldn't do that, it's wrong. It's taking advantage of PHP. Bah! We’re going to do it anyways. And FOR THE LOVE OF GOD, do not do this in production code. If you need multi-threading, use a different language.

Here's the three parts of the series:

• PHP Dark Arts: Multi-Processing (Part 1) (Introduction)
• PHP Dark Arts: Multi-Processing (Part 2) (Priority and Signals)
• PHP Dark Arts: Multi-Processing (Part 3) (Shared memory segments)

If you'd like to download the source he's created during these three posts, you can grab it here.