How can I downgrade from PHP 7 to PHP 5.6 on Ubuntu 16.04? [duplicate]

Today I got again problem with PHP 7 running despite I have disabled php7.0 apache module: phpinfo was showing php 7 using fastCGI …
… So if after you follow the below instructions you face this situation, you may need to disable the proxy_fcgi apache module:

sudo a2dismod proxy_fcgi proxy; sudo service apache2 restart

1. Re-Install PHP 5.6

What worked for me was this guide: http://www.lornajane.net/posts/2016/php-7-0-and-5-6-on-ubuntu

Actually is not required to remove php7.0, you can install php5.6 together ( also because you will have dependency problem with phpmyadmin package that required php7.0)

Assuming libapache2-mod-php is a suitable way to enable PHP in Apache for you, you can proceed in this way:

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-mbstring php7.0-mbstring php-xdebug libapache2-mod-php5.6 libapache2-mod-php7.0

2. Switch PHP version:

• From php5.6 to php7.0:
  • Apache:

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

  • CLI:

    sudo update-alternatives --set php /usr/bin/php7.0
    

• From php7.0 to php5.6:
  • Apache:

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

  • CLI:

    sudo update-alternatives --set php /usr/bin/php5.6