ubuntu 20.04 is using php 7.0 code example

Example 1: 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

Example 2: install php ubuntu 20.04

sudo apt install software-properties-common
sudo add-apt-repository ppa:ondrej/php

sudo apt update

sudo apt install -y php7.4