无法从Facebook PHP SDK 4的FacebookRedirectLoginHelper（）获取会话

我尝试了几十种解决方案，但无法使用PHPSDK4从Facebook获得会话。下面是我正在使用的两个页面（我以前尝试过单页面代码，但现在已经将它们拆分为两个页面）。重定向页面从不返回$\u会话，$SESSION变量始终为空。我将感谢任何帮助，谢谢

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不管问题是什么，它都源于使用子域。好奇是否有人知道为什么会这样？

//loginFB.php
include 'vendor/autoload.php';

ob_start();
session_start();

// added in v4.0.5
use Facebook\FacebookHttpable;
use Facebook\FacebookCurl;
use Facebook\FacebookCurlHttpClient;
// added in v4.0.0
use Facebook\FacebookSession;
use Facebook\FacebookRedirectLoginHelper;
use Facebook\FacebookRequest;
use Facebook\FacebookResponse;
use Facebook\FacebookSDKException;
use Facebook\FacebookRequestException;
use Facebook\FacebookOtherException;
use Facebook\FacebookAuthorizationException;
use Facebook\GraphObject;
use Facebook\GraphSessionInfo;

$id = '???';
$secret = '???';
FacebookSession::setDefaultApplication($id, $secret);

$helper = new FacebookRedirectLoginHelper('http://facebook.example.com/handleFB.php');

echo 'There is no current session, please login here: ';
echo '<a href="' . $helper->getLoginUrl( array( 'email', 'user_friends' ) ) . '">Facebook</a>';

//handleFB.php
include 'vendor/autoload.php';

session_start();

// added in v4.0.5
use Facebook\FacebookHttpable;
use Facebook\FacebookCurl;
use Facebook\FacebookCurlHttpClient;
// added in v4.0.0
use Facebook\FacebookSession;
use Facebook\FacebookRedirectLoginHelper;
use Facebook\FacebookRequest;
use Facebook\FacebookResponse;
use Facebook\FacebookSDKException;
use Facebook\FacebookRequestException;
use Facebook\FacebookOtherException;
use Facebook\FacebookAuthorizationException;
use Facebook\GraphObject;
use Facebook\GraphSessionInfo;

$id = '???';
$secret = '???';

FacebookSession::setDefaultApplication($id, $secret);

$helper = new FacebookRedirectLoginHelper('http://facebook.example.com/handleFB.php');

try {
  $session = $helper->getSessionFromRedirect();
} catch(FacebookRequestException $ex) {
  // When Facebook returns an error
    echo 'error1';
} catch(\Exception $ex) {
  // When validation fails or other local issues
    echo 'error2';
}
if ($session) {
  echo 'Yeah!!';
}

var_dump($_SESSION);

var_dump($session);