Facebook SDK 4.0 using app access token to publish_actions - permission missing when querying user_id/permissions

Question

I am currently updating an older Facebook app to version 4.0 of the Facebook PHP SDK. The app simply posts messages to the user's wall, thus requesting the publish_actions permission from the user. Since the app has not yet been submitted for app review, I am testing with a developer account and one test user account.

When I log in to the test user account and open the app, the app checks whether the publish_actions permission has been granted. In my scenario, this works fine for the test user:

FacebookSession::setDefaultApplication($config['appId'], $config['secret']);

$helper = new FacebookCanvasLoginHelper();
try {
  $session = $helper->getSession();
} catch(FacebookRequestException $ex) {
  // When Facebook returns an error
} catch(\Exception $ex) {
  // When validation fails or other local issues
}

if($session) { //When app installed
    $request_perm = new FacebookRequest($session, 'GET', '/me/permissions');
    $response_perm = $request_perm->execute();
    $graphObjectPermissions = $response_perm->getGraphObject()->asArray();

    $permissions = [];
    foreach ($graphObjectPermissions as $key => $permObject) {
        $permissions[$permObject->permission] = $permObject->status;
    }

if(array_key_exists('publish_actions', $permissions) && $permissions['publish_actions']=='granted'){
    echo "Permission granted!";
}

However, when I log in to the developer account and query the permissions of the test user with GET user_id/permissions, the returned graphObject does not contain the permission publish_actions at all (only email and public profile).

array ( 'email' => 'granted', 'public_profile' => 'granted', )

This is the code for the request, $access_token contains the app access token of my app.

$thisSession = new FacebookSession($access_token);
$request_perm = new FacebookRequest($thisSession, 'GET', '/' . $data['user_id'] . '/permissions');
$response_perm = $request_perm->execute();
$graphObjectPermissions = $response_perm->getGraphObject()->asArray();
$permissions = [];//create permissions array

foreach ($graphObjectPermissions as $key => $permObject) {
    $permissions[$permObject->permission] = $permObject->status;
}
var_export($permissions);

What do I need to change/do in order to check the publish_actions permission from the developer account using GET user_id/permissions?