I have had my iPhone for a little under a year and I have gone through countless chargers. From my understanding, don't quote me on this, apple chargers are made cheap so they mess up easily which makes you have to go out and buy another one. My advise is to buy another charger. Second, see if there is any dirt or debris in the charger port on your device. If there is, clean it out by using a small folded strip of paper or something just as small (BE VERY CAREFUL AND GENTLE!!!).
On buying new chargers, I would advise going online to buy a bundle of chargers for a decent price.
It is the charger. If it were the device itself, the charger would only be useless with that device and not the others.