Downgrade PHP 7.1/2 to 7.0 on Laravel Forge

run the follwoing as root

apt-get install -y --allow-downgrades --allow-remove-essential --allow-change-held-packages \
php7.0-cli php7.0-dev \
php7.0-pgsql php7.0-sqlite3 php7.0-gd \
php7.0-curl php7.0-memcached \
php7.0-imap php7.0-mysql php7.0-mbstring \
php7.0-xml php7.0-zip php7.0-bcmath php7.0-soap \
php7.0-intl php7.0-readline php-xdebug php-pear php7.0-fpm

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

sed -i "s/error_reporting = .*/error_reporting = E_ALL/" /etc/php/7.0/cli/php.ini
sed -i "s/display_errors = .*/display_errors = On/" /etc/php/7.0/cli/php.ini
sed -i "s/memory_limit = .*/memory_limit = 512M/" /etc/php/7.0/cli/php.ini
sed -i "s/;date.timezone.*/date.timezone = UTC/" /etc/php/7.0/cli/php.ini

service nginx restart

echo "xdebug.remote_enable = 1" >> /etc/php/7.0/mods-available/xdebug.ini
echo "xdebug.remote_connect_back = 1" >> /etc/php/7.0/mods-available/xdebug.ini
echo "xdebug.remote_port = 9000" >> /etc/php/7.0/mods-available/xdebug.ini
echo "xdebug.max_nesting_level = 512" >> /etc/php/7.0/mods-available/xdebug.ini
echo "opcache.revalidate_freq = 0" >> /etc/php/7.0/mods-available/opcache.ini

sed -i "s/error_reporting = .*/error_reporting = E_ALL/" /etc/php/7.0/fpm/php.ini
sed -i "s/display_errors = .*/display_errors = On/" /etc/php/7.0/fpm/php.ini
sed -i "s/;cgi.fix_pathinfo=1/cgi.fix_pathinfo=0/" /etc/php/7.0/fpm/php.ini
sed -i "s/memory_limit = .*/memory_limit = 512M/" /etc/php/7.0/fpm/php.ini
sed -i "s/upload_max_filesize = .*/upload_max_filesize = 100M/" /etc/php/7.0/fpm/php.ini
sed -i "s/post_max_size = .*/post_max_size = 100M/" /etc/php/7.0/fpm/php.ini
sed -i "s/;date.timezone.*/date.timezone = UTC/" /etc/php/7.0/fpm/php.ini

printf "[openssl]\n" | tee -a /etc/php/7.0/fpm/php.ini
printf "openssl.cainfo = /etc/ssl/certs/ca-certificates.crt\n" | tee -a /etc/php/7.0/fpm/php.ini

printf "[curl]\n" | tee -a /etc/php/7.0/fpm/php.ini
printf "curl.cainfo = /etc/ssl/certs/ca-certificates.crt\n" | tee -a /etc/php/7.0/fpm/php.ini

sudo phpdismod -s cli xdebug

sed -i "s/user = www-data/user = forge/" /etc/php/7.0/fpm/pool.d/www.conf
sed -i "s/group = www-data/group = forge/" /etc/php/7.0/fpm/pool.d/www.conf

sed -i "s/listen\.owner.*/listen.owner = forge/" /etc/php/7.0/fpm/pool.d/www.conf
sed -i "s/listen\.group.*/listen.group = forge/" /etc/php/7.0/fpm/pool.d/www.conf
sed -i "s/;listen\.mode.*/listen.mode = 0666/" /etc/php/7.0/fpm/pool.d/www.conf

service nginx restart
service php7.0-fpm restart

update v-hosts

update the nginx config for each v-host to use the correct php version

fastcgi_pass unix:/var/run/php/php7.0-fpm.sock;

reload nginx

sudo service nginx reload

Thanks to https://gist.github.com/Alymosul/da31c2e1b377b23780db29f21368761d