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

# php -v (default PHP version)

# From PHP 8.0 to PHP 7.4:
sudo a2dismod php8.0
sudo a2enmod php7.4
sudo update-alternatives --set php /usr/bin/php7.4
sudo service apache2 restart

# From PHP 7.4 to PHP 8.0:
sudo a2dismod php7.4
sudo a2enmod php8.0
sudo update-alternatives --set php /usr/bin/php8.0
sudo service apache2 restart