A huge number of today’s web sites use PHP as a development language / platform for dynamic web content. A significant amount of it running on Linux / Apache web server platforms. With Windows Server 2008, there are significant improvements to running PHP on Windows.
See this article “Tuning Windows Server 2008 for PHP“.
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
Some blogs have referenced (see this post) studies and test have reported that PHP runs 130% faster on Windows Server 2008.