public function getClasses($server)
    {
        $classes = [];

        if ($search = $this->search($server, '(&(objectClass=*))', ['objectclass'])) {
            $entries = $this->getEntries($search);
            foreach ($entries as $objectClass) {
                if (isset($objectClass['objectclass'])) {
                    unset($objectClass['objectclass']['count']);
                    $classes = array_merge($classes, $objectClass['objectclass']);
                }
            }
        }

        return array_unique($classes);
    }