How can I set PHP 7.2 under Debian 10?

I’m trying to install phpBB and am getting that 7.3 is too new to be supported, with a suggestion of downgrading to 7.2.

Am I correct that I want to downgrade PHP to 7.2, and if so, what are the preferred methods? aptitude does not appear to offer a php7.2 complement of functions.

I might be able to install from source, but if that’s the best option I see, I probably don’t see the best option.

How can / should I make PHP 7.2 available to phpBB, whether through making a parallel PHP 7 installation or some other means?

Thanks,