Concurrent Project Versions

I have a project using Yii that will have improvements as it grows.

I would like to be able to run multiple versions of my software on one server.

This would allow every user to use the same login screen.

The idea behind this is because I have beta customers which will always be using my latest version. Most users will be on the stable version.

I currently have a different database for each customer.

I also have command line cron jobs that run in the background.

As well there is a public module which will always be on the latest version.

Just wondering of how I might be able to direct yii to use specific versions of my code based on the user.

Thanks for any ideas.