How to save your iPhone for a while?

Say I want to save an iPhone for a while (around 5 Years+) , is there a special way like putting it in a fire, water, air proof box because I still want it to be usable in the far future.

I would say the danger to your phone siting for 5 years would be the battery if anything. If you could remove the battery it would protect it from possible corrosion caused by that. However, other than the battery failing I would think the phone would be usable in 5 years. Corrosion is your enemy here so it needs to stay dry. Perhaps in a sealed container with a big package of silica gel