Over the years PHP has gotten better and better running on Windows and IIS. The latest version of PHP for Windows includes dramatic improvements that come from a deep collaboration between the PHP Core Maintainers and Microsoft.
If you want to easily install PHP on Windows, you can use the newly released Microsoft Web Platform Installer to get the public community version of PHP ((VC6 x86 non thread safe installer build) on Windows XP/Vista/Server 2003/Server 2008/Win 2012/Win7 with IIS and the Microsoft Web Platform. The Windows Installer for PHP also automatically configures IIS FastCGI as part of its setup.
To install PHP using Web Platform Installer: