我没有得到Facebook PHP SDK 5.0.0的访问权限

Question

My code on the login page:

require ABSPATH . 'wp-content/plugins/fb_group/Facebook/autoload.php';

    session_start();

$fbData = array(
    'app_id' => 'XXX',
    'app_secret' => 'XXX',
    'default_graph_version' => 'v2.2'
);

$fb = new Facebook\Facebook($fbData);

    $params = array('req_perms' => 'publish_actions');
$helper = $fb->getRedirectLoginHelper();
$loginUrl = $helper->getLoginUrl('http://www.XXX.de', $params);


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

This is working. I get the link and the user is redirecting. But the code on the callback-page is not working:

require ABSPATH . 'wp-content/plugins/fb_group/Facebook/autoload.php';

    session_start();

$fbData = array(
    'app_id' => 'XXX',
    'app_secret' => 'XXX',
    'default_graph_version' => 'v2.2'
);

$fb = new Facebook\Facebook($fbData);


$helper = $fb->getRedirectLoginHelper();

$accessToken = $helper->getAccessToken();

echo '<p>' . $accessToken . '</p>';

I checked FB Docs and many tutorials but I get no accesstoken: https://developers.facebook.com/docs/php/gettingstarted http://www.tricksofit.com/2015/08/get-facebook-access-token-using-php-sdk-v5#.WNzQ62O5J7S

What I'm doing wrong?