I stumbled upon this article that I thought developers running PHP based web sites may be interested in. The authors write:
A significant percentage of web sites utilize PHP as a platform for dynamic content. During the development of Windows 2008, Microsoft included improvements that enable PHP to run more efficiently than previous Windows releases. This article describes how to tune Windows 2008, IIS 7.0 and PHP for environments with a single site and high concurrent user traffic
Read more at “Tuning Windows Server 2008 for PHP”.