Suggestions wanted for best practice - SaaS CMS

[eluser]otherjohn[/eluser]
Hi all, I am building a SaaS cms and have decided on using CI for the project.
Basically, we are building a multisite cms (SaaS) and will have:
Multiple domains each with their own site
all running on one app and one DB

So, i figured I would pair up all data with a "Site ID" which is grabbed as app launches. The question is what point should I grab this and how should I pass it on for all other use (routes, db calls,etc).

Should I hook it into the first hook and store it in a global var, or should I do something else like grab it on each route and possibly put the "getSiteID" in the route file (it would need a DB call).

Or are these silly ways to do something much easier to do?

Looking for best performance practice on this one. Any ideas?

Thanks
John

[eluser]cmgmyr[/eluser]
I have done this same thing. I have a "domains" table and within all of the other tables I have a "domain_id" index. When loading the application I have a "startup" library that runs a number of functions, the main one being find the current URL, matching it up to the DB, and getting that domain_id. The domain_id is saved to a session so that I can easily get to it later. Throughout the whole application I use the domain_id to pull the template location for their website files and their information from the database. You definitely don't want to put that domain_id in the URL's.

I hope that helps and if you have any other questions, please let me know.

-Chris

[eluser]Vheissu[/eluser]
The open source CMS Halogy supports multi sites on the one installation: http://www.halogy.com/ - it's built on Codeigniter too. You might find the code useful for ideas on how they handled multi sites.