I stumbled on this question while trying to achieve this, inside a Kubernetes environment.

The question, docker-style is opened here https://github.com/phpmyadmin/docker/issues/253.
I read it. Works with pure docker, but not 100% applicable to k8s though.

With k8s, the $document_root can't be mounted inside the nginx container, as it is strictly inside phpmyadmin container (the /var/www/html).
So nginx fails to serve the static parts.

PHP code is well served by the FPM, no problem with that, I receive a 200 OK
GET /index.php HTTP/1.1" 200 3600
But every other resources end up with a 404 as they are not served by the FPM (not his job), nor by nginx (it doesn't have them locally).

My question would be :
How to achieve this usecase [nginx] -> [phpmyadmin:fpm] in a Kubernetes environement

Corollary question :
Is there something wrong in my approach, or in my conf ?

For reference:

nginx.conf

    server {
      listen      80;
      server_name pma.exemple.com;

      location ~ /.*\.php$ {
        fastcgi_split_path_info ^(.+\.php)(/.+)$;
        fastcgi_index index.php;
        fastcgi_pass  backend-phpmyadmin-service:9000;
        include       fastcgi_params;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_param PATH_INFO $fastcgi_path_info;
      }
    }

deployment-pma.yaml

[...]
      containers:
        - name: backend-phpmyadmin
          image: phpmyadmin/phpmyadmin:fpm-alpine
          env:
            - name: PMA_HOST
              value: backend-mariadb
            - name: PMA_PORT
              value: '3306'
            - name: PMA_ABSOLUTE_URI
              value: 'http://pma.exemple.com/'
            - name: MYSQL_ROOT_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: backend-mariadb-secret
                  key: pass

service-pma.yaml

apiVersion: v1
kind: Service
metadata:
  name: backend-phpmyadmin-service
[...]
  ports:
  - protocol: TCP
    port: 9000