I have tried various methods to try to retrieve the POST data from the $_POST variable, but it is always empty when I post the form to the iframe in my facebook app. I have googled everything I could find and have tried the following methods. P3P headers, posting to the canvas url, posting to a direct url on my site with fb_sig* query parameters both in the query string and as hidden values in the form. None of these methods has worked. Does anyone have a simple example of an iframe page with a simple form that when posted just echos the POST data back on submit?