apache2 - How do I purge PHP 7, install PHP 5.6, and still get phpMyAdmin?

I have a local testing machine, with a fresh install of Ubuntu Mate 16.10. The default PHP installation is PHP 7. However, I need to run php 5.6 in order to keep inline with the servers I develop for.

I tried to remove PHP 7 and install PHP 5.6 using the instructions in this answer, as well as this answer.

It seemed I could have both PHP 7 and 5.6 installed side by side, but switch Apache to use PHP 5.6, but after attempting to have this set up, there were problems. I may be wrong, but it appeared that Apache was still connecting to some PHP 7 modules, or at the very least the PHP 5.6 installation was not fully successful. Whatever was happening, my sites were breaking.

So, I thought I might try to purge PHP 7, but, that took away some modules that I wanted to keep, such as phpMyAdmin. If I try to install just phpMyAdmin via apt-get, I get PHP 7 modules installed.

I'm afraid my tinkering has left my system in a bit of a mess, so I'd like to clean things up and start fresh. To that end, I'd like to purge PHP 7, install PHP 5.6, and install phpMyAdmin.

Or, at the very least, I need to have a system that works exactly like the servers I develop for, where PHP 5.6 is installed (in other words, purging PHP 7 is not the goal, making PHP 7 not interfere in any way with PHP 5.6 is). How can I get that to happen?

UPDATE:

After following some advice in the comments, I have a functioning PHP 5.6 environment that allows my sites to run on my local testing machine the same way they do on the servers.

phpMyAdmin also seems to be installed, by which I mean I have intalled it via apt-get on the command line and the installation went without errors. But it is not working. When I load up phpMyAdmin, I just get a blank screen.

Various sites I've been to suggest that the solution should be to run sudo apt-get install --reinstall phpmyadmin, sudo apt install php-gettext, or sudo dpkg-reconfigure phpmyadmin, but none of these helped. Right now, I don't know if phpMyAdmin is broken because of a conflict between PHP 7 and PHP 5.6, or if there is some other issue.