public function friendshipsLookup($userIds = null, $screenNames = null)
{
// redefine
$userIds = (array) $userIds;
$screenNames = (array) $screenNames;
// validate
if (empty($userIds) && empty($screenNames)) {
throw new Exception('Specify an userId or a screenName.');
}
// build parameters
$parameters = null;
if (!empty($userIds)) {
$parameters['user_id'] = implode(',', $userIds);
}
if (!empty($screenNames)) {
$parameters['screen_name'] = implode(',', $screenNames);
}
// make the call
return $this->doCall('friendships/lookup.json', $parameters, true);
}