public function searchUsers($searchTerm = null, $organization = null,
                                $requiredRoles = null, $hasAllRequiredRoles = null, $includeSubOrgs = true, $limit = 0, $offset = 0)
    {
        $result = array();
        $url = self::makeUserUrl($organization, null,
            array('q' => $searchTerm,
                  'requiredRole' => $requiredRoles,
                  'hasAllRequiredRoles' => $hasAllRequiredRoles,
                  'includeSubOrgs' => $includeSubOrgs,
                  'limit' => $limit,
                  'offset' => $offset));
        $data = $this->service->prepAndSend($url, array(200, 204), 'GET', null, true, 'application/json', 'application/json');
        if (!empty($data)) {
            $users = json_decode($data);
            foreach ($users->user as $user) {
                $result[] = @new UserLookup(
                    $user->username,
                    $user->fullName,
                    $user->externallyDefined,
                    $user->tenantId
                );
            }
        }
        return $result;
    }