Screaming Penguin - Source Does Matter

zez.org has a nice (yet very high level) tutorial on using IPC via PHP. I had no idea this was even possible and yet again PHP has functions (avail with certain compile time options) to handle it.

So why IPC? Here is a noteworhty part from the article, not the how, but the conclusion:

There're several applications for IPC, 
from the simple action to keep a parsed
 configuration file shared between processes to advanced engines and authentication systems. 
I've used this  extensions to optimize a
 bottle-neck in a web site keeping a big file 
that all the scripts  needed to read in memory,
 you can find some problems that might be solved using this or even create powerful applications
 with this in mind. 

For more info checkit via the link.   IPC PHP: zez.org