我正在尝试使用php sdk这样获取Facebook用户ID

$fb = new Facebook\Facebook([
    'app_id' => '11111111111',
    'app_secret' => '1111222211111112222',
    'default_graph_version' => 'v2.4',
]);

$helper = $fb->getRedirectLoginHelper();


$permissions = ['public_profile','email']; // Optional permissions
$loginUrl = $helper->getLoginUrl('http://MyWebSite', $permissions);

echo '<a href="' . $loginUrl . '">Log in with Facebook!</a>';


    try {
        $accessToken = $helper->getAccessToken();
        var_dump($accessToken);
    } catch (Facebook\Exceptions\FacebookResponseException $e) {
        // When Graph returns an error
        echo 'Graph returned an error: ' . $e->getMessage();
        exit;
    } catch (Facebook\Exceptions\FacebookSDKException $e) {
        // When validation fails or other local issues
        echo 'Facebook SDK returned an error: ' . $e->getMessage();
        exit;
    }

    if (!isset($accessToken)) {
        if ($helper->getError()) {
            header('HTTP/1.0 401 Unauthorized');
            echo "Error: " . $helper->getError() . "\n";
            echo "Error Code: " . $helper->getErrorCode() . "\n";
            echo "Error Reason: " . $helper->getErrorReason() . "\n";
            echo "Error Description: " . $helper->getErrorDescription() . "\n";
        } else {
            header('HTTP/1.0 400 Bad Request');
            echo 'Bad request';
        }
        exit;
    }

// Logged in
    echo '<h3>Access Token</h3>';
    var_dump($accessToken->getValue());

// The OAuth 2.0 client handler helps us manage access tokens
    $oAuth2Client = $fb->getOAuth2Client();

// Get the access token metadata from /debug_token
    $tokenMetadata = $oAuth2Client->debugToken($accessToken);
    echo '<h3>Metadata</h3>';
    var_dump($tokenMetadata);

// Validation (these will throw FacebookSDKException's when they fail)
    $tokenMetadata->validateAppId($config['11111111111']);
// If you know the user ID this access token belongs to, you can validate it here
//$tokenMetadata->validateUserId('123');
    $tokenMetadata->validateExpiration();

    if (!$accessToken->isLongLived()) {
        // Exchanges a short-lived access token for a long-lived one
        try {
            $accessToken = $oAuth2Client->getLongLivedAccessToken($accessToken);
        } catch (Facebook\Exceptions\FacebookSDKException $e) {
            echo "<p>Error getting long-lived access token: " . $helper->getMessage() . "</p>\n\n";
            exit;
        }

        echo '<h3>Long-lived</h3>';
        var_dump($accessToken->getValue());
    }

    $_SESSION['fb_access_token'] = (string)$accessToken;

但是它给了我这个错误：

Facebook SDK returned an error: 
Cross-site request forgery validation failed. 
The "state" param from the URL and session do not match.

请任何帮助，我是php的新手，也感谢Facebook sdk的任何帮助。