Automatic switch for solar charger

Hello all. I’m New to the forum and arduino. I have a problem and wanted to know if there are any practical solutions.

I have an iPhone and a solar batter charger (see link below). The charger needs to be manually switched from charging itself (in the sun) to charging my iPhone.

Question: is there a switch that can be made to trigger the charger based on how much light is being shown on the trigger? Example, in full sun, charge the solar charger, in pitch black, charge my phone.

Phone is always connected via USB.

http://www.amazon.com/gp/aw/d/B00DLUYSPO/ref=mp_s_a_1_1?qid=1401138595&sr=8-1#

Please delete. I posted in sensors section but can't delete this post. Sorry for the duplicate.