I was looking for a way to pass session data between subdomains on the same PHP server. I found this useful article at madCarrot:
http://www.madcarrot.co.uk/2005/08/pass_sessions_b.html
Nice looking lady in the picture, too 
[LATER EDIT]
It seems I was not able to make it work like that unfortunately… however the solution I came to was like this:
1) create as many virtual hosts as you like - either subdomains or totally different domains (more…)
I was looking at this portofolio…
http://www.byraul.net/portfolio
and I noticed a very interesting site made by that guy
http://www.onlinecronjobs.com/
The site lets you define an online cron job, in case your hosting company does not allow you to use cron jobs on the server. Ingenious, I would say, cool ideea.
Pay respect to your customer by talking to him, allowing him to understand the underlying mechanisms of your website programming and by implementing his requirements directly in your code, using his own words for class names, variables and methods. Pay respect to your fellow programmers by writing beautiful code, so they can also understand what you are doing in php.
In this article…
Dorian Mladin just finished implementing a site where you can buy pizza online in TIMISOARA!
Here is the link:
http://www.pizzanapoleon.ro
I’m looking at the pictures right now and they look sooo tasty! I’m happy to see this site online, because it is the first real life implementation of katyshop that I know about. Thank you for keeping the “engine by katyshop” in the footer of the site and thank you for the feedback.