Some problems in the use of php

Because the work in progress needs to use PHP7.4 version, but nix does not support PHP7.4, is there any way to install and use it by yourself? And how do I open PHP’s rewirte function on nixos? can someone help me?

i have root, i think its will be useful

I used the method inside GitHub - techcode1001/replit_root: This is how to get root permissions in replit. to get the full root (actually fake root, it’s more like a virtual machine because it becomes a Debian system), and then installed php7.4, but I don’t know how to make the program run in php7.4, can anyone help me?