installing php 7.3 with php 7.4 ubuntou20.04 code example
Example: install php 7.4 on ubuntu 20.04
sudo apt update
sudo apt install php7.4
sudo apt install php7.4-common php7.4-mysql php7.4-xml php7.4-xmlrpc php7.4-curl php7.4-gd php7.4-imagick php7.4-cli php7.4-dev php7.4-imap php7.4-mbstring php7.4-opcache php7.4-soap php7.4-zip php7.4-intl -y