Nginx as reverse proxy , rewrite or proxy pass request to docker container

Question

I'm trying to use nginx as reverse proxy in front of a few applications which are on the same machine(Docker containers). As a test, I tried to connect PHPmyAdmin to a URI like: www.example.com/phpma

This is how my location block looks like:

    location /phpma/ {
    proxy_pass         http://192.168.2.23:8081/;
    proxy_redirect     off;
    proxy_set_header   Host $host;  
    }

Everything works fine until you try to login or out.

Lets say when you put your username & pass and click login button, application redirects you to the home page. The URL is like :

https://example.com/index.php?route=/&route=%2F

Now, user faces an error, because the actual url from user side should have the /phpma uri added to the redirect link. Lets say the above url should be like:

https://example.com/phpma/index.php?route=/&route=%2F

How can we overcome a situation like this, or in a production environment how we should design our application to address this? Thanks