Get Facebook user email upon registration - php

Question

I'm trying to allow users to register on my web application via Facebook. As part of my normal registration users must supply their email address, and I need to include this as part of the Facebook registration.
I am using the code below, which works correctly, except it doesnt return the user email address as part of Facebook's response. I am aware I need to specifically "ask" for the email, but I'm confused where/how I do this in my code below?
I am also aware a user may choose to not supply their email address as part of the process, but I'm able to handle that.
// Grab our facebook details
$app_id = $this->config->item('fb_app_id');
$app_secret = $this->config->item('fb_secret_key');
$my_url = $this->config->item('fb_url');
session_start();
if(isset($_REQUEST["code"]))
{
$code = $_REQUEST["code"];
}
else
{
$_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='" . $dialog_url . "'</script>");
}
if ((isset($_REQUEST['state'])) && (($_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));
if ( ! empty($user))
{
// NO EMAIL HERE?!
$email = strtolower($user->email);
}
}

Answer 1

Looks like this has been asked before. The answer can be found here:
Facebook Graph API, how to get users email?

Answer 2

This code works for me...Hopefully it will work well for you also
define('FACEBOOK_APP_ID', 'YOUR_APP_ID_HERE');
define('FACEBOOK_SECRET', 'YOUR_APP_SECRET_HERE');
// No need to change function body
function parse_signed_request($signed_request, $secret) {
list($encoded_sig, $payload) = explode('.', $signed_request, 2);
// decode the data
$sig = base64_url_decode($encoded_sig);
$data = json_decode(base64_url_decode($payload), true);
if (strtoupper($data['algorithm']) !== 'HMAC-SHA256') {
error_log('Unknown algorithm. Expected HMAC-SHA256');
return null;
}
// check sig
$expected_sig = hash_hmac('sha256', $payload, $secret, $raw = true);
if ($sig !== $expected_sig) {
error_log('Bad Signed JSON signature!');
return null;
}
return $data;
}
function base64_url_decode($input) {
return base64_decode(strtr($input, '-_', '+/'));
}
if ($_REQUEST) {
$response = parse_signed_request($_REQUEST['signed_request'],
FACEBOOK_SECRET);
/*
echo "<pre>";
print_r($response);
echo "</pre>"; // Uncomment this for printing the response Array
*/
$email = $response["registration"]["email"];