# Predefined Constants

Memcache Constants
Name | Description
--- | ---
`MEMCACHE_COMPRESSED` (int) | Used to turn on-the-fly data compression on with Memcache::set(), Memcache::add() and Memcache::replace().
`MEMCACHE_HAVE_SESSION` (int) | 1 if this Memcache session handler is available, 0 otherwise.
`MEMCACHE_USER1` (int) | Used to turn user-defined application flag on with Memcache::set(), Memcache::add() and Memcache::replace().
`MEMCACHE_USER2` (int) | Used to turn user-defined application flag on with Memcache::set(), Memcache::add() and Memcache::replace().
`MEMCACHE_USER3` (int) | Used to turn user-defined application flag on with Memcache::set(), Memcache::add() and Memcache::replace().
`MEMCACHE_USER4` (int) | Used to turn user-defined application flag on with Memcache::set(), Memcache::add() and Memcache::replace().