1. Първо малко действие :)
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.
2. Switch PHP version:
From php5.6 to php7.0 :
Apache:
sudo a2dismod php5.6 ; sudo a2enmod php7.0 ; sudo service apache2 restart
CLI:
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