Can't Authenticate in IE - session

Question

I've been a Facebook developer for a while now, but I'm starting fresh with the new Facebook App layout and stuck one of the first steps. So apparently my old method of authentication doesn't work anymore.
To solve this, I tried the one given as an example at http://developers.facebook.com/docs/authentication/ . However, it doesn't seem to work at all on internet explorer.
Here's my code right below:
<?php
$app_id = "-----";
$app_secret = "------";
$my_url = "http://apps.facebook.com/myapp/";
require('facebook-php-sdk-2343fca/src/facebook.php');
$facebook = new Facebook(array(
'appId' => $app_id,
'secret' => $app_secret,
'cookie' => true,));
$session = $facebook->getSession();
session_start();
$code = $_REQUEST["code"];
echo $_REQUEST['state']." == ".$_SESSION['state'];
if(empty($code)) {
$_SESSION['state'] = md5(uniqid(rand(), TRUE)); //CSRF protection
$dialog_url = "http://www.facebook.com/dialog/oauth?client_id="
. $app_id . "&redirect_uri=" . urlencode($my_url) . "&state="
. $_SESSION['state'] . '&scope=publish_stream,read_stream,user_photos,friends_photos,user_events,friends_events';
echo("<script> top.location.href='" . $dialog_url . "'</script>");
}
if($_REQUEST['state'] == $_SESSION['state']) {
$token_url = "https://graph.facebook.com/oauth/access_token?"
. "client_id=" . $app_id . "&redirect_uri=" . urlencode($my_url)
. "&client_secret=" . $app_secret . "&code=" . $code;
$response = file_get_contents($token_url);
$params = null;
parse_str($response, $params);
$graph_url = "https://graph.facebook.com/me?access_token="
. $params['access_token'];
$user = json_decode(file_get_contents($graph_url));
//echo("Hello " . $user->name);
//My app goes here!
} else {
echo("The state does not match. You may be a victim of CSRF.");
}
?>
So far, all I know is the problem has to do with $_SESSION['state'];
Any help would be much obliged!

Answer 1

Hmm, I got it working. It's a quite obscure issue with P3P cookies handling by Internet Explorer with iframes. In short, just put this somewhere in the beginning of your code:
header('P3P:CP="IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT"');
You can read more here: How to properly handle session and access token with Facebook PHP SDK 3.0?