How to Switch between Multiple PHP Version and install phpmyadmin on Ubuntu 12.04,14.04 and 16.04

How to Switch between Multiple PHP Version and install phpmyadmin on Ubuntu 12.04,14.04 and 16.04
Install PHP 5.6 on Ubuntu
Use the following set of command to add PPA for PHP 5.6 in your Ubuntu system and install PHP 5.6.

sudo apt-get install python-software-properties
sudo add-apt-repository ppa:ondrej/php
sudo apt-get update
sudo apt-get install -y php5.6

Check Installed PHP Version:

php -v 

PHP 5.6.29-1+deb.sury.org~xenial+1 (cli)
Copyright (c) 1997-2016 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2016 Zend Technologies
with Zend OPcache v7.0.6-dev, Copyright (c) 1999-2016, by Zend Technologies

Install PHP 7.1 on Ubuntu
Use the following set of command to add PPA for PHP 7.1 in your Ubuntu system and install PHP 7.1.

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

Check Installed PHP Version:

php -v 

PHP 7.1.0-5+deb.sury.org~xenial+1 (cli) ( NTS )
Copyright (c) 1997-2016 The PHP Group
Zend Engine v3.1.0-dev, Copyright (c) 1998-2016 Zend Technologies
with Zend OPcache v7.1.0-5+deb.sury.org~xenial+1, Copyright (c) 1999-2016, by Zend Technologies

Switch PHP version:

From php5.6 to php7.1:

sudo a2dismod php5.6 ; sudo a2enmod php7.1 ; sudo service apache2 restart

From php7.1 to php5.6:

sudo a2dismod php7.1 ; sudo a2enmod php5.6 ; sudo service apache2 restart

How to install phpmyadmin on PHP7 Apache/2.4.7 (Ubuntu)?

Install it via wget and create an alias in Apache. Keep track:
Change to directory /usr/share:

cd /usr/share

Change to root user:

sudo su

Download phpMyAdmin:

wget https://files.phpmyadmin.net/phpMyAdmin/4.5.4.1/phpMyAdmin-4.5.4.1-all-languages.zip

Unzip it: (you may install unzip first)

unzip phpMyAdmin-4.5.4.1-all-languages.zip

Rename the folder:

mv phpMyAdmin-4.5.4.1-all-languages phpmyadmin

Change permissions:

chmod -R 0755 phpmyadmin

Configure apache so that it can find it correctly:

gedit /etc/apache2/sites-available/000-default.conf

Anywhere after "DocumentRoot /var/www/html" insert these line:

Alias /phpmyadmin "/usr/share/phpmyadmin/"

     Order allow,deny
     Allow from all
     Require all granted

Restart Apache:

service apache2 restart

In order to test that our system is configured properly for PHP, we can create a very basic PHP script.
We will call this script info.php. In order for Apache to find the file and serve it correctly, it must be saved to a very specific directory, which is called the "web root". In Ubuntu 16.04, this directory is located at /var/www/html/. We can create the file at that location by typing:

sudo nano /var/www/html/info.php

This will open a blank file. We want to put the following text, which is valid PHP code, inside the file:

<?php
phpinfo();
?>

When you are finished, save and close the file.
The address you want to visit will be:

http://your_server_IP_address/info.php
OR
http://localhost/info.php