Since I've created the phpMyAdmin container for Docker I've always felt strange about using PHP's built in web server there. It really made it poor choice for any production setup and probably was causing lot of problems users saw with this container. During the weekend, I've changed it to use more complex setup with Supervisor, nginx and PHP FPM.
As building this container is one of my first experiences with Docker (together with Weblate container), it was not as straightforward as I'd hope for, but in the end is seems to be working just fine. While touching the code, I've also improved testing of the Docker container to tests all supported setups and to better report in case of test fails.
The nice side effect of this is that the PHP code is no longer being executed under root in the container, so that should make it more sane for production use as well (honestly I never liked this approach that almost everything is executed as root in Docker containers).