Is It Safe To Leave An IPhone On Charge All Night?

I need to film my room all night for a ghost thing! Is it safe to have my Iphone 4s on charge all night while on the video Camera?

Absolutely!

Yup, the battery is designed to prevent overcharging

You won't have problems with battery but with overheating of iPhone. Try recording for a hour and then take it in your hand and fell the heat.

There was an EU law passed a while ago to have all chargers as USB due to their ability to not overcharge or cause problems such as the O2 phone issue many moons ago due to their charger problems and reports of them blowing up.