(PECL memcached >= 0.1.0)
Memcached::casByKey — Compare and swap an item on a specific server
Memcached::casByKey() is functionally equivalent to
Memcached::cas(), 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.
Unique value associated with the existing item. Generated by memcache.
The key identifying the server to store the value on.
The key under which to store the value.
The value to store.
The expiration time, defaults to 0. See Expiration Times for more info.
TRUE on success or
FALSE on failure.
The Memcached::getResultCode() will return
Memcached::RES_DATA_EXISTS if the item you are trying
to store has been modified since you last fetched it.