Speeding up your PHP database application
A sheet over at talks.php.net shows you how to speed up your PHP database application using a practicable example. An actual real-world setup (Ubuntu, Apache, PHP5, MySQL) is used for this benchmark.
By the use of conventional techniques such as APC, query caching, direct MySQL queries, persistent database connections, the number of possible script hits per second could be raised from 17 to over 1100.
Source: Talks.PHP.Net: OsCon 2006 Sheets (2006-08-01 02:40:40)