(PECL memcached >= 0.1.0)
Memcached::setMultiByKey — Store multiple items on a specific server
Memcached::setMultiByKey() is functionally equivalent to Memcached::setMulti(), except that the free-form server_key can be used to map the keys from items to a specific server. This is useful if you need to keep a bunch of related keys on a certain server.
成功时返回 TRUE， 或者在失败时返回 FALSE. 如需要则使用 Memcached::getResultCode()。