Getting facebook user access token / PHP SDK 3.1.1 - facebook

Question

since this article is not answering the question ( How to get user access token? ), I wanted to ask how to get the user access token.
I already have my app access token, easy. I also saw in the latest php sdk Base_facebook class there is an getUserAccesstoken function, but its useless because in the end you only get the app access token.
This is my authentification flow:
user gets into the fanpage app, and at some point, he has to authorize permissions:
$facebook = new Facebook(array(
'appId' => $app_id,
'secret' => $secret,
'cookie' => true
));
$user = $facebook->getUser();
if($user == 0) {
$login_url = $facebook->getLoginUrl($params = array('scope' => "publish_stream", 'redirect_uri' => "https://www.facebook.com/pages/PAGENAME/PAGE-ID?sk=app_APP-ID0&app_data=af"));
echo ("<script> top.location.href='".$login_url."'</script>");
}
This works, fine, app_data "af" param is set to get back the page inside the fanpage app.
Because I realize, that when I remove the app, and get back to the auth page, the user cookie ($user) is still set and so the user wont be asked for permissions again.
For that reason I wanted to check permissions as well, and therefore I need the user access token
try{
$permissions = $facebook->api("/me/permissions", 'GET', array('access_token' => "$access_token" ));
}
catch (Exception $e) {echo ("<script> top.location.href='".$login_url."'</script>"); }
if( array_key_exists('publish_stream', $permissions['data'][0]) ) {
// Permission is granted!
} else {
echo ("<script> top.location.href='".$login_url."'</script>");
}
So I tried the server side auth example (https://developers.facebook.com/docs/authentication/server-side/), but of course this won't work here as you are not able to read the $_REQUEST from inside the app, so I am gonna stuck here. - How do you guys check for the permission inside an app?
$app_id = "YOUR_APP_ID";
$app_secret = "YOUR_APP_SECRET";
$my_url = "YOUR_URL";
session_start();
$code = $_REQUEST["code"];
if(empty($code)) {
$_SESSION['state'] = md5(uniqid(rand(), TRUE)); //CSRF protection
$dialog_url = "https://www.facebook.com/dialog/oauth?client_id="
. $app_id . "&redirect_uri=" . urlencode($my_url) . "&state="
. $_SESSION['state'];
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);
}
else {
echo("The state does not match. You may be a victim of CSRF.");
}
TIA & cheers,
daniel

Answer 1

See the section of the Facebook Developer Docs about Server-Side authentication: https://developers.facebook.com/docs/authentication/server-side/
Or you can use a hybrid client-server authentication:
http://developers.facebook.com/blog/post/534/