public function friendshipsDestroy($userId = null, $screenName = null)
{
// validate
if ($userId == '' && $screenName == '') {
throw new Exception('Specify an userId or a screenName.');
}
// build parameters
if ($userId != null) {
$parameters['user_id'] = (string) $userId;
}
if ($screenName != null) {
$parameters['screen_name'] = (string) $screenName;
}
// make the call
return $this->doCall('friendships/destroy.json', $parameters, true, 'POST');
}