Uninstall php 7 in ubuntu 18.04

This will remove all php7 versions, be it php 7.0 or php 7.1 etc..

sudo apt-get purge php7.*
sudo apt-get autoclean
sudo apt-get autoremove

• apt/apt-get autoclean → cleans obsolete deb-packages, less than clean
• apt/apt-get autoremove → removes orphaned packages which are not longer needed from the system, but not purges them, use the --purge option together with the command for that.

**To Install PHP again **

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

if php7.0

sudo apt-get install php7.0

if php7.1

sudo apt-get install php7.1

if php7.2

sudo apt-get install php7.2

To switch that to the newer 7.1,7.2,7.3,7.4 version, first disable older PHP version:

user@test:~# sudo a2dismod php7.0

Then enable PHP 7.2:

user@test:~# sudo a2enmod php7.2
sudo service apache2 restart

Install all the required extension, so it won't make any error in future. Replace command based on your version. I used 7.2 as I have installed that version.

sudo apt install php7.2-common php7.2-mysql php7.2-xml php7.2-xmlrpc php7.2-curl php7.2-gd php7.2-imagick php7.2-cli php7.2-dev php7.2-imap php7.2-mbstring php7.2-opcache php7.2-soap php7.2-zip php7.2-intl -y

This will remove PHP

sudo apt-get purge `dpkg -l | grep php7.2| awk '{print $2}' |tr "\n" " "`
sudo apt-get purge php7.*
sudo apt-get autoremove --purge
whereis php
sudo rm -rf /etc/php

Firstly you need to restart the apache to take all in effect and also You can install mutliple php version using this post or just using

sudo apt update
sudo apt-add-repository ppa:ondrej/php
sudo apt update
sudo apt install -y php5.6 php5.6-cli php5.6-common

disable php7.2:

sudo a2dismod php7.2

enable php 5.6:

sudo a2enmod php5.6

After all restart the apache again to take into affect

service apache2 restart

Just run

sudo apt-get purge 'php*'