While ibiblio is not able to support use of phpMyAdmin, we do not forbid it as long as (a) it is kept up to date, and (b) access is restricted using HTTP Basic Auth or similar on the directory in which it is installed. If you are having trouble setting up a web app, our most common advice is to start simple and build up. If your document root is at /public/vhost/e/example/html/ and your domain is example.org for example, you might make a directory like /public/vhost/e/example/html/apptest with a plain HTML index.hmtl file and confirm you can reach it at example.org/apptest. If that works, then you replace your index.html with an index.php and a Hello World in PHP to confirm that that works, and so on.
Taking a step back, it’s not obvious that you need phpMyAdmin if what you are trying to do is make simple changes or insertions to your database. We have client tools installed on the login host. If you want to run a graphical tool against your database, you can tunnel traffic from your local host through the login host to the database host. We are willing and able to support you if you have specific access issues setting up an SSH tunnel to access your database.