Pointing Fingers At yoU Laughing
This means that something is so funny, you'd be pointing at them laughing. However, you can use this term to depict something that is funny, without the pointing fingers part. So if you wanted to use it instead of the very commonly-used "Lol", then go ahead and do it!
I saw this facebook picture of Andrew's Halloween costume and it looked so funny, so I typed him a comment which said, "PFAUL".