How to transfer data between domains and subdomains?

Question

Sessions

Hello.
I ran into a problem when transferring data from one subdomain to another (or from the main domain to a subdomain).
If you write data to a session, then when you switch to another subdomain, they are lost, as they remain in another session of the subdomain (as I understand it). All data transfer is scheduled for an unauthenticated user.
Please tell me how to do it right?
Thanks in advance to all who respond!

Answer 1

It is correct to write the session domain as .domain.tld.