multiple versions of php on Ubuntu Xenial 16.04 down grade to php5.6 from php7

gistfile1.txt

# reference1:  https://by-example.org/ubuntu-16-04-xenial-downgrade-php-7-to-php-5-6/
# reference2: https://askubuntu.com/questions/761713/how-can-i-downgrade-from-php-7-to-php-5-6-on-ubuntu-16-04/761735 
# reference2 (recommended)

sudo add-apt-repository ppa:ondrej/php

sudo apt-get update

sudo apt-get install php7.0 php5.6 php5.6-mysql php-gettext php5.6-mbstring php-xdebug libapache2-mod-php5.6 libapache2-mod-php7.0

# from php5 to php7
sudo a2dismod php5.6 ; sudo a2enmod php7.0 ; sudo service apache2 restart

# from php7 to php5 
sudo a2dismod php7.0 ; sudo a2enmod php5.6 ; sudo service apache2 restart

sudo update-alternatives --config php