Hello,
I'm interested by your project since I have been using PHP for more than 8 years now and I have a great experience with APIs. I have worked with, among others, the Google Maps API, the Facebook, Instagram, Twitter API and Freebase API just to name a few.
I took a look at your SO subject, read the code and I have one question : have you successfully managed to do something with your code with Aweber or not ? It's to know if your project is mainly about getting the API to work or giving the API the right data or both. Anyway, I can start right now on your project.
Best regards,
Laurent.