MultiSite - shared user login - J15 and J3 site?

Hello, is it possible to share users/login between two different Joomla versions? The basic idea is a "delayed" or step-by-step migration from a J15 site to a J3 site. So, keeping the major site features and extensions on the "old" J15 site… but already creating a new application in the new J3 site. This new content (directory with user submissions) could be a subdomain, until the rest of the site and functionality is migrated.

In short:

- J15 main site with CB register and different applications
- link to new J3 site where the same users can submit content in a new extension and application

The reason is not to add something to the old site, just add the functionality to the new J3 site. The other content will be migrated later on.

Any ideas or experiences?

CB has no multiple site features. I'm not sure if the multisite extensions for Joomla will work between Joomla versions like that. You could keep them in sync probably with a bunch of external query actions, but I've no idea how well that'll work and it'll require query actions to handle usergroup mapping, registration, etc..

extensions.joomla.org/extensions/core-enhancements/multiple-sites/14863

but be warned this is a complex endeavour

Yep, I am aware of the complexity or that it takes a specialized 3rd-party extension i.e. MightySites, JMS Multi Sites etc. JMS SSIDomains seems very interesting, too. But it is for Logins only, no user sharing.

Probably the biggest issue or even showstopper is the possible difference in users J15 <-> J3. Maybe Session and password related stuff as well.

In regards of MightySites, it seems to work by sharing of the user tables: The "slave" J3 site would have to pull data from the J15 site! Could not find a suitable topic in their forum… but i guess that it will be the main problem.

Anyway, this is just an alternative idea that raised in my mind. Maybe we have to go the usual full migration route…

the interesting thing about mighty sites, is that it allows you to chose which db threads to share
on which site

not sure if the j!_users table will share effectively though

good luck either way