Why is the first request to a Facebook IFrame App Canvas Page a POST request?

Question

I noticed when I set up my first FB app today (an iframe app accessed within facebook) that all the requests made to it via facebook are HTTP POSTs rather than GET requests. Is there any reason for this? What if I wanted to implement HTTP caching?

I'm new to developing on the FB platform, forgive me if this is an obvious question but I've googled and can't find the answer.

Bicipital

Answer 1

Facebook POSTs to the initial page in order to pass along the signed request that includes potentially important information for the application.

Preliminary

Thanks for your answer. I'll have to experiment and see if all requests to the app are posts. – Bicipital

Just the initial page load. Navigation within your app won't trigger POST requests, as they're just happening within the iframe. – Preliminary