SHELL

ubuntu update php 7.4 to 8

sudo apt-get purge php7.*
# recommended 
sudo apt-get autoclean
sudo apt-get autoremove
sudo add-apt-repository ppa:ondrej/php
sudo apt-get update
# end recommended 
sudo apt-get install php8.0

ubuntu upgrade php to 7.3

sudo apt-get install software-properties-common
sudo add-apt-repository ppa:ondrej/php
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install -y php7.3