If you just request php7.0, it'll install Apache as default. Do apt-get install php7.0-fpm and it'll install as FPM instead, leaving something like nginx up to you.
php7.0
apt-get install php7.0-fpm
Use the command:
sudo apt install php7.2 php7.2-common php7.2-cli php7.2-fpm
It will require the php7.2 dependencies in strict mode (WITHOUT apache2).
On Ubuntu 18.04 I managed to do this successfully with:
sudo apt-get install php7.2-cli