Memcached if a free and open source distributed memory object caching system. It is used by web applications to lower database load by caching data in a key-value format for faster retrieval. If you happen to develop on Mac OS X, you can easily setup a development memcached server locally using MacPorts.
sudo port install memcached
Easy enough… Now, you can start the server by running
Memcached is listening on port 11211.
One thing that memcached is used for is storing PHP sessions (memcached is distributed, rememer?) In order to do that, you must edit php.ini and set
session.save_handler = memcache
session.save_path = tcp://localhost:11211
Don’t forget to enable the memcahe.so extension and restart your Apache server.
Now, you can start storing data in memcache from your web app. If you wish/need to debug the value of a given key, you can simply do so using telnet
telnet localhost 11211