(PECL memcached >= 2.0.0)
Memcached::deleteMultiByKey — Elimina varios elementos de un servidor específico
   Memcached::deleteMultiByKey() es funcionalmente idéntica
   al método Memcached::deleteMulti(), excepto que
   el argumento server_key puede ser utilizado para asociar
   las claves keys con un servidor específico.
  
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.
keysLas claves a eliminar.
timeEl tiempo de espera del servidor antes de eliminar los elementos.
Nota: As of memcached 1.3.0 (released 2009) this feature is no longer supported. Passing a non-zero
timewill cause the deletion to fail. Memcached::getResultCode() will returnMEMCACHED_INVALID_ARGUMENTS.
   Returns an array indexed by keys. Each element
   is true if the corresponding key was deleted, or one of the
   Memcached::RES_* constants if the corresponding deletion
   failed.
   
   The Memcached::getResultCode() will return
   the result code for the last executed delete operation, that is, the delete
   operation for the last element of keys.
  
