PHP 7.2 for Ubuntu

1. Add PPA ondrej/php

sudo add-apt-repository ppa:ondrej/php
sudo apt update

2. Current PHP packages

dpkg -l | grep php | tee packages.txt

3. Install PHP 7.2

sudo apt install php7.2 php7.2-common php7.2-cli php7.2-fpm

If you are using Apache with prefork MPM (type apachectl -V to see the MPM used), you’d need to install libapache2-mod-php7.2 instead of php7.2-fpm.

4. Install additional modules

Take a look at the packages.txt file we created at step #2

5. Web server configuration

Apache with php-fpm

a2disconf php7.1-fpm
a2enconf php7.2 

Apache with mod_php

a2dismod php7.1 (or your current version)
a2enmod php7.2

6. Remove old versions

sudo apt purge php7.1*

Source: https://ayesh.me/Ubuntu-PHP-7.2