My iPhone 4 won't turn on after being left outside?

I left my iPhone 4 outside while I was sunbathing the other day and since then it won't turn on, I've tried connecting it to my computer, tried charging it but no luck.

Added (1). I've also tried the hold home and lock button, also didn't work.

Hold the lock button and the home button in at the same time

Ah man, the person above me clearly didn't even read the question… Annoys me. Anyways, sorry looks like you will have to bring it in and get it fixed. You have tried everything, as it sounds.

It may be that the battery has over heated and failed, you can buy these online if your able to fit it yourself or by all means email me as we repair iphones and can have a look for you