Display Won't Turn On No Matter What

I was recently at a party all fine and everything but when I pulled my phone out of my pocket it was a black screen so I though oh so it's probably dead I'll plug it in and it keeps making the "plugged in" sound every 10 seconds and I plugged it into iTunes and everything works and says it's a working phone but I tried DFU mode I tried Hard Restart nothing is seeming to work what do I do? I gave it to my friend to work on it what should he do to check and make the screen work again