phpvm is a very simple PHP version manager / switcher. It's a bash script, and it allows us to switch between installed (with Homebrew) PHP versions on macOS.
git clone https://github.com/sptmru/phpvm && cd phpvm
sudo cp phpvm.sh /usr/local/bin/phpvm
sudo chmod +x /usr/local/bin/phpvm
phpvm <version>, for example: phpvm 8.0, phpvm 7.4. Quite simple :)