PHP 7.4 reached end of life on 28 Nov 2022 and is no longer being updated. It's strongly recommended to upgrade to the latest version as soon as possible. You can read the official PHP migration guide here.
sudo apt update
sudo add-apt-repository ppa:ondrej/php
sudo apt install php7.4
sudo apt install php7.4-cli php7.4-json php7.4-common php7.4-mysql php7.4-zip php7.4-gd php7.4-mbstring php7.4-curl php7.4-xml php7.4-bcmath
php -v
php -m
echo '<?php phpinfo(); ?>' | sudo tee /var/www/html/info.php
http://your_server_ip/info.php