Support for Drupal 7 is ending on 5 January 2025—it’s time to migrate to Drupal 10! Learn about the many benefits of Drupal 10 and find migration tools in our resource center.
A HOWTO on Optimizing PHP was initially pointed out in this forum topic. The article describes how to optimize PHP in a variety of settings. It also includes a nice discussion on caching.
For people who are setting up servers, or who are interested in learning more about how Drupal can run more efficiently, this article is a good read.