(PECL memcached >= 0.1.0)
Memcached::replace — Replace the item under an existing key
Memcached::replace() is similar to Memcached::set, but the operation fails if the key does not exist on the server.
The key under which to store the value.
The value to store.
The expiration time, defaults to 0. See Expiration Times for more info.
Returns TRUE on success or FALSE on failure. The Memcached::getResultCode will return Memcached::RES_NOTSTORED if the key does not exist.