Introduction

The version of phpmyadmin for ubuntu doesn’t play nice with php 7.2. The problems were fixed in newer versions of phpmyadmin.

The Fix

Just a few steps and things will be fixed.

First visit www.phpmyadmin.net and download the latest version. My example is version 4.8.1.
> cd /tmp
> wget https://files.phpmyadmin.net/phpMyAdmin/4.8.1/phpMyAdmin-4.8.1-all-languages.zip

Unzip and rename the folder.
> unzip phpMyAdmin-4.8.1-all-languages.zip
> mv phpMyAdmin-4.8.1-all-languages phpmyadmin

Backup the old version of phpmyadmin and move over the new version.
> mv /usr/share/phpmyadmin /usr/share/phpmyadmin.save
> mv phpmyadmin /usr/share/

Edit /usr/share/phpmyadmin/libraries/vendor_config.php and make the following change.

Change

define('CONFIG_DIR', '');

define('CONFIG_DIR', '/etc/phpmyadmin/');

That’s it.

Conclusion

This is a bug that will eventually get fixed.