There are many ways to share a photo with another iPhone. For example, you can email the photo, send it as an iMessage, share it using AirDrop, or share it in a PhotoStream.
When you are viewing the photo on your iPhone, tap the Sharing icon (the square with the arrow coming out the top) in the bottom left corner of the screen. This will bring up the sharing screen where you can select the method you wish to use to share the photo.
Posted in: Photos