I am playing in a world in Survival Mode. I have known that Zombie Pigmen drop gold and even golden swords when killed. I expect to spawn at night like regular non-friendly mobs. But they don't seem to ever spawn at night.
I even tried trapping a pig in with a zombie because I was that desperate! So what are the conditions necessary to be able for Zombie Pigmen to spawn? Do I have set my difficulty level to hard or something?