As your site traffic grows it takes longer and longer to generate a dynamic page from sending multiple queries to a database. One possible solution to limit queries is to cache the result of each query that is needed, or to have a complete full page cache for your site.

The purpose of this article is to help with ways of caching your PHP powered site. It only touches very briefly on using Cache_Lite (part of PEAR), APC (part of PECL) and developing your own solution. Ideally it should be used in such a way that if your database server goes down it also acts as something to fall back on.

Article: Caching PHP pages