While Virtualmin does support having multiple PHP versions on Debian, it’s no where near as simple as doing so in CentOS.
CentOS includes a special repository of packages designed to work side-by-side with those available in CentOS by default.
It’s super-simple to set that up, in CentOS.
Debian doesn’t have any PHP packages designed to work alongside existing ones… so unfortunately the only way to do this would be to build and maintain the PHP packages yourself.
My recommendation would probably be to upgrade to Debian 8, if you’re simply looking for a newer PHP version.
However, note that you should still be able to run phpMyAdmin on your server, you’d just need to use one of the versions that works with your distro/version.
Thanks Eric. I’m aware that there’s no way in Debian to have multiple releases of PHP installed directly from the standard repositories. However, I was wondering: Does Virtualmin simply query the package management for php to find separate releases, or does it search the path or else? Is it possible to have a self-installed PHP eg in /opt/php55 and make Virtualmin recognize it?