Abra um terminal
cd /etc/apache2/mods-enabled
sudo a2dismod php5
sudo rm php5.load
sudo rm php5.conf
sudo a2enmod php7.0
sudo ln -s php7.0.conf ../mods-available/php7.0.conf
sudo ln -s php7.0.load ../mods-available/php7.0.load
sudo a2enconf php7.0-cgi
sudo a2enconf php7.0-fpm
# do those commands only if the above didn't work out
sudo ln -s php7.0-cgi.conf ../conf-available/php7.0-cgi.conf
sudo ln -s php7.0-fpm.conf ../conf-available/php7.0-fpm.conf
sudo service apache2 restart