passing custom parameters to facebook fan page tab
Facebook passes in your data as part of the signed_Request data.Here is how you would retrieve it using PHP:
<?php require 'facebook.php';$app_id = "YOUR APP ID HERE";$app_secret = "YOUR SECRET KEY HERE";$facebook = new Facebook(array( 'appId' => $app_id, 'secret' => $app_secret, 'cookie' => true));// THE MAGIC SAUCE$signed_request = $facebook->getSignedRequest();$page_id = $signed_request["page"]["id"];$like_status = $signed_request["page"]["liked"];// HERE IS A STRING OF YOUR APP DATA.$app_data = $signed_request["app_data"];echo '$app_data = '.$app_data;?>This example requires the Facebook PHP api and will write your app_data into the browser window where you can marvel in all its glory.
Oh wow, I didn't know about the app_data parameter.
Here's another method for whatever it's worth:
http://iamskwerl.com/tech/2011/11/passing-query-variables-to-facebook-fan-page-tabs/
There is a solution available although I have not tried it but hope it works http://ikorolchuk.blogspot.com/2011/03/facebook-fan-page-pass-parameter-to.html