If you have an older 30 pin cable you can get lightning adapters for them. There are two that are available from Apple:
This one is the cheaper of the two but it has the disadvantage of not working if your iPhone is in a case. The added thickness of the case keeps the contacts of the connector in making contact with the connections in the receptacle.
This adapter works even if your phone is in a case or not. Of course it's going to cost a little more than the precious one, but it's worth it.
Another possibility is getting a Belkin lightning cable:
They work great and I haven't had any issues with them.