Building on my experience of setting up Phorge on php7.4 with Debian 11 (Bookworm).
Most modern OSes' distributions do not keep php7.4 available, as it is officially EOL on PHP upstream.
There's little information in the documentation about installing PHP on a system - which is surely on purpose, as there are many tutorials on "how to set up a LAMP server" and all its variants.
Someone installing Phorge would likely know where to look to do so, as we're clear about what's necessary to get Phorge running, and the packages are normally universal.
However, installing an EOL version of PHP is nontrivial, and requires either third-party package archives (e.g., PPA's, DPA's, AUR) or building PHP from source.
Sometimes, these third-party archives can bring in conflicts and other danger and trouble with your local package state, and make a big mess.
For instance, adding deb.sury.org for their maintained php7.4 forward-port, meant that apt wanted to install apache2, despite already having nginx available.
The workaround took a lot of trial and error to find, and this issue had kept me from using Phorge after a necessary server upgrade.
This is all rendered moot with the implementation of PHP 8 support, but until that is the case, we're in a weird limbo.
This is mostly a note to myself to go in and touch the docs, and to others on how to tame the dragons which be here; but also a request for thoughts on how best to approach this, if even at all.
I can spin up some testing VMs with common server OS targets, and walk myself through the practice of setting up Phorge and php7 on each, take notes, and write the procedures down.
This is rendered moot by D25537: Update PHP versions in install guide: Remove 5, Add 8. and by further discussion in this task's comment thread - PHP 8 is de facto supported, and installing PHP 7 should be unnecessary.
I'll consider this task closed.