You can also install multiple PHP versions on your system and switch PHP version between them. Also, you can configure Apache VirtualHosts to use different-2 PHP versions.

Install PHP 7.4 on Ubuntu

PHP 7.4 is the latest stable version is available for installation. Use the following set of commands to enable PPA for PHP 7.4 in your Ubuntu system and install it. You can use this version for production use also.

sudo apt-get install software-properties-common
sudo add-apt-repository ppa:ondrej/php
sudo apt-get update
sudo apt-get install -y php7.4

Now use the following command to check installed php version on your system.

php -v 

PHP 7.4.5 (cli) (built: Apr 28 2020 14:49:23) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies
    with Zend OPcache v7.4.5, Copyright (c), by Zend Technologies

Install PHP 7.3 on Ubuntu

PHP 7.3 stable version has been released. Use the following set of commands to enable PPA for PHP 7.3 in your Ubuntu system and install it. You can use this version for production use also.

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

Now use the following command to check installed php version on your system.

php -v 

PHP 7.3.9-1+ubuntu16.04.1+deb.sury.org+1 (cli) (built: Sep  2 2019 12:54:04) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.3.9, Copyright (c) 1998-2018 Zend Technologies
    with Zend OPcache v7.3.9-1+ubuntu16.04.1+deb.sury.org+1, Copyright (c) 1999-2018, by Zend Technologies

Install PHP 7.2 on Ubuntu

PHP 7.2 stable version has been released. Use the following set of commands to enable PPA for PHP 7.2 in your Ubuntu system and install it. You can use this version for production use also.

sudo apt-get install software-properties-common
sudo add-apt-repository ppa:ondrej/php
sudo apt-get update
sudo apt-get install -y php7.2

Now use the following command to check installed php version on your system.

php -v 

PHP 7.2.16-1+ubuntu18.04.1+deb.sury.org+1 (cli) (built: Mar  7 2019 20:23:29) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies
    with Zend OPcache v7.2.16-1+ubuntu18.04.1+deb.sury.org+1, Copyright (c) 1999-2018, by Zend Technologies

Install PHP 7.1 on Ubuntu

Use the following set of commands to add PPA for PHP 7 in your Ubuntu system and install PHP 7.1 version.

sudo apt-get install software-properties-common
sudo add-apt-repository ppa:ondrej/php
sudo apt-get update
sudo apt-get install -y php7.1

Now use the following command to check installed php version on your system.

php -v 

PHP 7.1.27-1+ubuntu18.04.1+deb.sury.org+1 (cli) (built: Mar  7 2019 20:02:25) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.1.0, Copyright (c) 1998-2018 Zend Technologies
    with Zend OPcache v7.1.27-1+ubuntu18.04.1+deb.sury.org+1, Copyright (c) 1999-2018, by Zend Technologies

Install PHP 7.0 on Ubuntu

Use the following set of commands to add PPA for PHP 7 in your Ubuntu system and install PHP 7.0 version.

sudo apt-get install python-software-properties
sudo add-apt-repository ppa:ondrej/php
sudo apt-get update
sudo apt-get install -y php7.0

Now use the following command to check installed php version on your system.

php -v 

PHP 7.0.33-5+ubuntu18.04.1+deb.sury.org+1 (cli) (built: Mar  8 2019 09:49:15) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2017 Zend Technologies
    with Zend OPcache v7.0.33-5+ubuntu18.04.1+deb.sury.org+1, Copyright (c) 1999-2017, by Zend Technologies

Install PHP 7 Modules

You may also need to install modules based on your application requirements. Use the following command to search available PHP 7 modules in the package repository.

sudo apt-cache search php7*

php-all-dev - package depending on all supported PHP development packages
php7.0 - server-side, HTML-embedded scripting language (metapackage)
php7.0-cgi - server-side, HTML-embedded scripting language (CGI binary)
php7.0-cli - command-line interpreter for the PHP scripting language
php7.0-common - documentation, examples and common module for PHP
php7.0-curl - CURL module for PHP
php7.0-dev - Files for PHP7.0 module development
php7.0-gd - GD module for PHP
php7.0-gmp - GMP module for PHP
...
...
...
php7.1-xml - DOM, SimpleXML, WDDX, XML, and XSL module for PHP
php7.1-xmlrpc - XMLRPC-EPI module for PHP
php7.1-zip - Zip module for PHP
php7.1-opcache - Zend OpCache module for PHP
php7.1 - server-side, HTML-embedded scripting language (metapackage)
php7.1-xsl - XSL module for PHP (dummy)
...
...
php7.2-bcmath - Bcmath module for PHP
php7.2-bz2 - bzip2 module for PHP
php7.2-cgi - server-side, HTML-embedded scripting language (CGI binary)
php7.2-cli - command-line interpreter for the PHP scripting language
php7.2-common - documentation, examples and common module for PHP
php7.2-curl - CURL module for PHP
php7.2-dba - DBA module for PHP

You can install the required PHP modules on your system as below command. Make sure to install packages for correct PHP version by specifying the version with the package name. Without defining the package version, it will install the latest package.

sudo apt-get install php7.2-mysql php7.2-curl php7.2-json php7.2-cgi php7.2-xsl

Congratulation! Enjoy the development with PHP 7.