(PECL memcached >= 0.1.0)
Store an item on a specific server
public bool Memcached::setByKey ( string $server_key, string $key, mixed $value [, int $expiration ] )
Memcached::setByKey() is functionally equivalent to Memcached::set(), except that the free-form server_key can be used to map the key to a specific server. This is useful if you need to keep a bunch of related keys on a certain server.
Paramete