# install
apt install php7.3-fpm
apt install nginx

# you need the mysql libraries to connect to mysqli(host, user, pass, instance)
apt install php7.3-mysql

# edit nginx to use php
nano /etc/nginx/sites-enabled/default


# Replace this:
        location / {
                # First attempt to serve request as file, then
                # as directory, then fall back to displaying a 404.
                try_files $uri $uri/ =404;
        }


# With:
		location ~ \.php$ {
			include snippets/fastcgi-php.conf;
			fastcgi_pass unix:/run/php/php7.3-fpm.sock;
		}


# create a hello file
nano /var/www/html/hello.php

# With contents:
<?php
        echo "hi";
?>

# restart nginx
/etc/init.d/nginx restart

# test
http://my-ip-here/hello.php

Debugging:

If you have issues connecting to your mysql database, make sure you create a php page with

<?php 
phpinfo(); 
?>

and ensure you have mysqli installed: