Cookie settings for session across WPML subdomains using custom AJAX login

Question

I am trying to enable a custom login session across both English and French subdomains.

-WordPress is installed only on domain.com.

-There are only en.domain.com and fr.domain.com as WPML subdomains, with redirects (as instructed here: https://wpml.org/faq/server-setting-for-languages-in-different-domains/).

-No issues with navigation across subdomains.

My AJAX custom login successfully signs in the user with wp_signon(). The AJAX request successfully returns 4 cookies. However, session is not initiated; on page refresh, user is still not connected.

When I login through /wp-login.php, the session is properly initiated.

It seems like the solution lies in the proper configuration of COOKIE_DOMAIN, COOKIEPATH & SITECOOKIEPATH settings:

define('COOKIE_DOMAIN', '.domain.com');
define('COOKIEPATH', '/');
define('SITECOOKIEPATH', '/');

Anyone has a solution for this?

Answer 1

I continued looking for an answer elsewhere, and found one.

Basically, the "cookie domain origin policy" was the issue, not sign-in process. I was calling domain.com/wp-admin/admin-ajax.php from a subdomain fr.domain.com.

I called fr.domain.com/wp-admin/admin-ajax.php instead, and that worked.