PHP and Memcache

Memcache is really a great caching system which we used recently in one of our site.

memcached is a high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load.

We used it on our site for displaying categories, products, searching, paging etc.... and it was very effective. The database load reduced drastically and pages loaded very fast. You just need a good memory on your server,

It is also relatively easy to implement memcache, While the server and API only have one way to get data from the cache, there exists 3 ways to put data in:
set -- unconditionally sets a given key with a given value
add -- adds to the cache, only if it doesn't already exist
replace -- sets in the cache only if the key already exists
Additionally, all three support an expiration time.