What's wrong with my iPhone 4S?

My iPhone 4S won't charge I've tried the computer and the wall outlet but it still doesn't work. I turned it off all last night when I woke up I put it on the charger while it was still of well it got turned on and it started to charge but i unplugged it because I had to go to school now it won't charge anymore what's wrong with it

Time to replace the battery.

Is the charger ok I had a problem with my charger with iOS 7 I would try charging it off using the computer it that doesn't work make a back-up then restore.