How to run Apache parallel to Nginx?

Question

Nginx

Good evening.
At the moment, I have Nginx running, which gives the Ghost blog for one domain. How can I install Apache on the same VPS and make it serve other PHP scripts under a different domain?
Thank you.

Answer 1

Alternatively, hang them on different IPs so that both processes can use port 80.
Or proxy Apache through nginx.
Why is this even necessary?