iPhone 5 purple lens flare is normal

 

This can happen when a light source is positioned at an angle (usually just outside the field of view) so that it causes a reflection off the surfaces inside the camera module and on to the camera sensor. Moving the camera slightly to change the position at which the bright light is entering the lens, or shielding the lens with your hand, should minimise or eliminate the effect.”
For what it’s worth, Pocket-lint is inclined to agree with Apple. Most cameras, be it those found on smartphones or even some DSLR cameras, will all suffer from some lens flare when shot at direct light. It’s not unique to Apple devices