How to Upgrade PHP to php7.2 and use Multiple PHP Rendition on Ubuntu 18.04

This tutorial will guide you to upgrade PHP to 7.2 from any past versions like 5.6 or 7.0. So you know you already understand the time for 5.6 and 7.0 passed out months ago. So let us plan to upgrade PHP to the latest ie 7.2. Which comes with several safety stains.