There appear to be two ways to pronounce the last syllable based on deeply held beliefs and cultural divides and assumptions:
- Phi fi fo fum
- Fee phi fo fum?
I've heard that (2) is the American pronunciation (as in the motor parts corp Delphi), although it's not how we pronounce it in my office in America, which is probably largely the result of the Russian programmer who introduced us to Delphi.
I'd say, I'd never pronounce the Greek "Phi" as as "fee", but I don't speak Greek and if I did, I would probably pronounce it wrong.