My iphone has stopped working

I was using my iphone last night night and it was working fine. I then put it next to my bed, still turned on, with 30+% battery, so it didn't die. This morning i tried to unlock it, and it didn't work.thinking it was dead, i plugged it int my ihome. I then left it alone all morning. I latter came back to check on it, and it still wouldnt turn on,. I held down the top button to see if the little charging sign came on the screen or if the connect to charger thing came on.nothing appeared like it is supposed to. So i switch it to a wall charger, and still nothing is working. What do you think happened and how can i fix it? I never dropped it or any thing, and the phone is pluggeed in all the way and plugged into the wall. I have tried everything i can think of besides going into the apple store. Is there anything else i shpould try before i take it there? Sorry this was long!

Added (1). My phone is a 4s and i got it at Christmas, so it isn't very old.

Try holding the home and lock button for 15 seconds.

Time for a new phone

Wow thats strange, is it really cold overnight where you live? Sometimes dramatically changing temps can ruin a battery. I would take it the apple store, let them check it.