PHP
You're going to need different versions
Totara Learning Solutions continues to support many versions of Totara Learn.
As such developers will need to be able to run, develop against, and test under multiple versions of PHP.
How you achieve this is up to you, and your decision will likely be based around your operating system of choice, and how comfortable you are with the different options out there.
Developers within the office already take a number of approaches, including using PHP-fpm and running on different ports, and docker.
What you'll need
From Totara 13 onwards the range of supported PHP versions can be found in the readme.md file in the source code.
See Totara PHP support for an example of PHP versions supported by previous releases.