+can be applied so that the key is deleted after that many seconds, but this
+will only work if you are using a 1.2.x server. If you are using a 1.2.x
+server and you want to use the expiration value, please call memcached_version
+one time for the memcached_st instance. If you don't do this no-reply and
+buffered mode will be disabled to avoid getting out of sync with the server.
+memcached_delete_by_key() works the same, but it takes a master key to
+find the given value.