Pronounced as it looks, ilp.
I like pie is supposed be random and funny, but it has become VERY predictable. It's most commonly used by 7-12 years olds, specifically 8-10 year olds.
girl1: *yawns* I'm bored.
girl1: what the heck?
girl2: It means I like pie.
girl1: oh that's awesome you're so amazing!
Mature person: Uh, yeah, i think i'll be going.