Versioning

Hello guys,

i have created my project with Codeigniter and i would like to create versioning.

The first page of my project is a login form.
The users have a version field in my database so depending on the user who has logged i would like to load the corresponding version of my project.

I have thought to use session, to change the variable $application_folder at index.php and rename the folder application with the available versions, but the index.php file has not loaded the Codeigniter yet.

How can i achieve that?

My project structure is the default by the Codeigniter and is like this

To be more clear my structure is

my project
    index.php ( $application_folder = '0.1'; )
    - system  
    - 0.1
        - cache
        - config
        - controllers
        ......
        - views
    - 0.2
        - cache
        - config
        - controllers
        ......
        - views
    - 0.3
        - cache
        - config
        - controllers
        ......
        - views