public function createCacheKey($keys) {
        if (is_array($keys)) {
            $key = array_shift($keys);

            if ($keys) {
                foreach ($keys as $value) {
                    if (is_array($value)) {
                        $key .= '-' . md5(json_encode($value));
                    } else if ($value) {
                        $key .= '-' . $value;
                    }
                }
            }
        } else {
            $key = $keys;
        }

        return (string) $key;
    }