Here's my latest:
Day 1: Chest/Tri's (alternate which one is trained first week to week)
Day 2: Back/Bi's (alternate which one is trained first week to week)
Day 3: Quads/Abs
Day 4: Shoulders/Forearms
Day 5: Calves/Hams
I know you asked for a 4 day PP split. I've tried one exactly like rippedtrojans, and I only found it good as a maintainence or cutting routine. If you're looking for a good mass routine that allows you to train every bodypart heavy, this one is really good.