I'm adding this here in case anyone else needs it. But mostly so I can "Google" it the next time I install Pi-hole on Apache.
Installing Pi-hole on an existing and working Apache web server on Raspberry Pi. This assumes you have set up your own static IP and whatnot.
- Run the Pi-hole install. When you get to "Do you wish to install the web server" select "Off".
- Finish the Pi-hole installation process. Do not panic.
- Run "sudo usermod -a -G pihole www-data"
- Install "sudo apt install php-sqlite3"
- At a minimum, restart Apache "sudo service apache2 restart" or reboot the Pi.