Alright, I happen to work at the Apple Genius Bar and I can tell you this is a pretty common issue we have. I can walk you through the most basic procedure that works 9/10 times for our guests.
First, you're going to want to go to Home Depot. Then you're going to want to buy a sledge hammer. Next, go home and place your iPhone on the ground. Smash it with the sledge hammer. Then, return to Home Depot. Return the sledge hammer for a refund - you no longer have any use for it. Now, use the money you just got from the sledgehammer and buy an inflatable pool. Now return home. Inflate your new pool and fill it with water - but make sure the water is exactly 98 degrees. Once the water has heated properly, its time to go to work. Slam dunk your now broken iPhone into the heated pool, make sure to get every single piece. Now, strip down and sit in the pool. Gently caress your iPhone. Get out of the pool and put some dry clothes on, take your broken iPhone to Apple and have them issue a replacement.
If you followed all the steps properly and to the letter, then your warranty should still be intact. Hope this helps!