I have never use ShapeShift and its API (I believe) before. However I am willing to take on this challenge and gain a brand new experience with PHP. Anyway I'd appreciate more information such as your website URL and how do you want the Bitcoin to be "withdrawn" - with a service?
The withdraw will just put it in my admin dashboard where I can see it and send them their withdrawal manually
Sound not much of a problem to me but also not an easy task. If you haven't get anyone started with it, kindly send me a private message containing more information.
As for the "admin dashboard", is it a custom coded one or a open-source script?