使用facebook SDK 4.0获取电子邮件

这是我的代码。我正在尝试获取用户电子邮件，但无法。昨天我收到了正确的电子邮件，但我错误地删除了文件。我现在缺少什么？

在login_fb.php中，我这样调用电子邮件：echo $_SESSION['email'];

session_start();
//added in v4.0.0
require_once 'autoload.php';
use Facebook'FacebookSession;
use Facebook'FacebookRedirectLoginHelper;
use Facebook'FacebookRequest;
use Facebook'FacebookResponse;
use Facebook'FacebookSDKException;
use Facebook'FacebookRequestException;
use Facebook'FacebookAuthorizationException;
use Facebook'GraphObject;
use Facebook'Entities'AccessToken;
use Facebook'HttpClients'FacebookCurlHttpClient;
use Facebook'HttpClients'FacebookHttpable;
//init app with app id and secret
FacebookSession::setDefaultApplication( '','' );
//login helper with redirect_uri
$helper = new FacebookRedirectLoginHelper('http://www.myurl/facebook/fbconfig.php' );
try {
    $session = $helper->getSessionFromRedirect();
} catch( FacebookRequestException $ex ) {
    //when facebook returns an error
} catch( Exception $ex ) {
    //when validation fails or other local issues
}
if (isset($session)) {
    $request = new FacebookRequest( $session, 'GET', '/me?locale=en_US&fields=name,first_name,last_name,email,gender' );
    $loginUrl = $helper->getLoginUrl( array(
        'scope' => 'email'
    ));  
    $response = $request->execute();
    //response
    $graphObject    = $response->getGraphObject();
    $fbid           = $graphObject->getProperty('id');          // Facebook ID
    $full_name      = $graphObject->getProperty('name');        // Facebook full name
    $first_name     = $graphObject->getProperty('first_name');  // Facebook first name
    $last_name      = $graphObject->getProperty('last_name');   // Facebook last name 
    $email          = $graphObject->getProperty('email');       // Facebook email
    $birthday       = $graphObject->getProperty('birthday');    // Facebook birthday
    $gender         = $graphObject->getProperty('gender');      // Facebook gender
    /* ---- session variables -----*/
    $_SESSION['fbid']       = $fbid;           
    $_SESSION['full_name']  = $full_name;
    $_SESSION['first_name'] = $first_name;
    $_SESSION['last_name']  = $last_name;
    $_SESSION['email']      = $email;
    $_SESSION['birthday']   = $birthday;
    $_SESSION['gender']     = $gender;
    /* ---- header location after session ----*/
    header("Location: ../login_fb.php");
} else {
    $loginUrl = $helper->getLoginUrl();
    header("Location: ".$loginUrl);
}