Unlike the hypernode-vagrant you can not just run hypernode-switch-php to change the PHP version. Because there is no systemctl to manage the services other steps must be performed. To switch to a different PHP version run the following commands:
# Edit /etc/my_init.d/60_restart_services.sh to use the correct PHP
vim /etc/my_init.d/60_restart_services.sh
# Change the enabled PHP
update-alternatives --set php $(which php7.1)
# Restart (all) services
bash /etc/my_init.d/60_restart_services.sh