I have one subdomain using codeigniter4 (which requires php7’ish) and a homegrown subdomain (using php5). Yes, php5 bad, hence the new codeigniter site. I have tried to get the sessions to work together, to no avail. What is the best way to troubleshoot the issue?

An example of what appear to be identical session cookies (in the same directory):

shows 2 session cookies with same number

I have code on both sites saying they both named PHPSESSID, and they seem to be tangled together (if I close one session the other site will be logged out also), but they are separate.

I’ve tried changing every setting I can think of. session_name() shows the same thing for both sites.