(PECL memcached >= 0.1.0)
Memcached::getDelayedByKey — Request multiple items from a specific server
$server_key
   , array $keys
   [, bool $with_cas
   [, callable $value_cb
  ]] )
   Memcached::getDelayedByKey() is functionally equivalent to
   Memcached::getDelayed(), except that the free-form
   server_key can be used to map the
   keys to a specific server.
  
server_keyThe key identifying the server to store the value on or retrieve it from. Instead of hashing on the actual key for the item, we hash on the server key when deciding which memcached server to talk to. This allows related items to be grouped together on a single server for efficiency with multi operations.
keysArray of keys to request.
with_casWhether to request CAS token values also.
value_cb
       The result callback or NULL.
      
   Returns TRUE on success or FALSE on failure.
   Use Memcached::getResultCode() if necessary.