sudo update-alternatives --config php

This brings up a prompt to interactively select the alternative PHP binary path that php points to.

There are 2 choices for the alternative php (providing /usr/bin/php).
Selection Path Priority Status

------------------------------------------------------------

* 0 /usr/bin/php8.0 80 auto mode
1 /usr/bin/php7.4 74 manual mode
2 /usr/bin/php8.0 80 manual mode

Press to keep the current choice[*], or type selection number:

To set the path without the interactive prompt:

update-alternatives --set php /usr/bin/php7.4