How to take pictures in the dark with an iPhone?
There are some apps that may help you with dark night photos (though I have no experience with these apps). Here you are:


NightCap: This app captures 15x more light to capture the best photos in low light situations. It also provides the best tools to help take the perfect shot day or night.
Camera Flash and Zoom: A full featured camera app with digital flash, 5x digital zoom, geotagging, preview before saving, quick and burst modes, and plenty more tools for night photography. 
Night fast Snap!: Very suitable for night photography, you can take 30 clear photos in 2 seconds in the case of low light. The app only fires the shutter when it detects the iPhone is steady to ensure sharpness.