How to implement common users for 2 sites?

Question

MODX

Good day!
Who has experience, tell me ....
Let's say there is a site.ru site (let's say on modx revo), you need to tie a store to it on the shop .site.ru subdomain on another cms, or on modx as well.
The goal is to have common users , that is, everything worked as one site
Question - 1) How to implement it?
2) Should I use one database or is it better to use different ones?
Thank you in advance!

Answer 1

How to implement it?

The technology is called " Single Sign-On ". Perhaps there are already implementations for your CMS, but if not, you can write it according to existing examples.
They also do this through " OAuth2 ", but for the connection of their own site and its subsite, this will be redundant. Usually it is built for authorization through completely third-party services over which there is no control. On the other hand, perhaps for your first engine there is already a ready-made plugin "OAuth2 Provider", and for the store "OAuth2 Consumer".
Doesn't really matter.

Answer 2

Rewrite the authorization / authentication module on another cms so that it takes session data from the first cms.