Facebook demo script issue - php

Question

I want that users can authenticate through their fb account, and i tried their demo script:
$app_id = "*****";
$app_secret = "*****";
$my_url = "http://localhost/fb/fb.php";
session_start();
$code = $_REQUEST["code"];
if(empty($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'];
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 " . $user->name);
echo "$user->name";
}
else {
echo("The state does not match. You may be a victim of CSRF.");
}
The problem is that after a successful login only the "Hello" string is displayed, but my $user->name is not showed.

Answer 1

Even though this is official FB code (I didn't realize that at the start, sorry), I recommend you debug it to see what goes wrong.
Activate error reporting
Remove the # in front of all calls - it suppresses the output of errors
Look what address $graph_url contains and whether you can access it in your browser
See whether the call to $graph_url works out (output the result)
See whether the json_decode() works out (output the result)
if this is a global or Facebook issue, you may need to talk to Facebook about what is wrong with their demo code.