--- a/web/callback.php	Mon Apr 15 12:59:52 2013 +0200
+++ b/web/callback.php	Mon Apr 15 13:04:10 2013 +0200
@@ -37,5 +37,10 @@
     /**
      * Mistaken request? Some malfeasant trying something?
      */
+    echo "<h2>$_GET</h2><pre>";
+	print_r($_GET);
+	echo "</pre><h2>$_SESSION</h2><pre>";
+	print_r($_SESSION);
+	echo "</pre>";
     exit('Invalid callback request. Oops. Sorry.');
 }