The server connection via port 443 fails when using PHP 8.1 or above about nginx-proxy HOT 2 CLOSED

This has absolutely nothing to do with nginx-proxy.

I compared:
php:8.0-apache which is using: curl 7.74.0
php:8.1-apache which is using: curl 7.88.1
(both really old btw)

And your reason seems to be a change in CURL:

Starting in commit 1a0ebf6632f8, to be released in curl 7.78.0, curl now treats the host name “localhost” specially and will use an internal “hard-coded” set of addresses for it – the ones we typically use for the loopback device: 127.0.0.1 and ::1. It cannot be modified by /etc/hosts and it cannot be accidentally or deliberately tricked by DNS resolves. localhost will now always resolve to a local address!

https://daniel.haxx.se/blog/2021/05/31/curl-localhost-as-a-local-host/

And because you are using .localhost in your DNS entry this is exactly what happens.

Try changing .localhost to something random like .ltd I just tested with your compose and that works fine.
Or use the name / alias of the docker container, as Docker DNS automatically makes internal entries for each service. So curl -v https://nginx-proxy points to your nginx-proxy container without adjusting anything manually.

from nginx-proxy.

@SchoNie Thank you for the detailed follow-up! I'll close the issue since it's not related to nginx-proxy.

from nginx-proxy.