Se deben seguir estos pasos luego de actualizar brew
brew install php@7.4
brew link --force php@7.4
brew services start php@7.4
export PATH="/usr/local/opt/php@7.4/bin:$PATH"
export PATH="/usr/local/opt/php@7.4/sbin:$PATH"
Fuente:
https://stackoverflow.com/a/64724216/2400373