Through the AUR it is possible to install older and newer PHP versions, simultaneously on the same system. I often had trouble installing using pacman and pamac so here's what I did:
mkdir -p $HOME/bin
mkdir ~/src
cd ~/src
git clone https://aur.archlinux.org/php72.git
cd php72
| /* | |
| _ _ _ _____ _ ____ _ | |
| | \ | | ___ | |_ | ___| | __ _ _ __ _ __ _ _ | _ \ _ _ ___| | __ | |
| | \| |/ _ \| __| | |_ | |/ _` | '_ \| '_ \| | | | | | | | | | |/ __| |/ / | |
| | |\ | (_) | |_ | _| | | (_| | |_) | |_) | |_| | | |_| | |_| | (__| < | |
| |_| \_|\___/ \__| |_| |_|\__,_| .__/| .__/ \__, | |____/ \__,_|\___|_|\_\ | |
| |_| |_| |___/ | |
| compiler : GCC | |
| command : gcc source.c -o FlappyBird.exe -Werror -Wall -W -s | |
| license : www.unlicense.org (Please credit my channel tho) |