Optimizing PHP, in which

we explain why optimizing PHP involves many factors which are not code related, and why tuning PHP requires an understanding of how PHP performs in relation to all the other subsystems on your server, and then identifying bottlenecks caused by these subsystems and fixing them. We also cover how to tune and optimize your PHP scripts so they run even faster.

This includes tips for PHP on IIS and Windows, as well as (of course) Apache and Unix.

Not to say that there’s nothing about writing code, either. I learned, for example, that references don’t provide performance benefits for non-object variables. In fact, they may hurt performance. Whaddya know.