On his IIS blog today Don Raman has posted a guide to working with the Microsoft SQL Server driver with PHP (on Windows).
Today I am going to explain basics of developing PHP application on Microsoft SQL Server. Let me start by stating one thing, developing PHP application on Microsoft SQL Server is really easy. The extension which glues the two world namely PHP and Microsoft SQL Server is called 'Microsoft SQL Server Driver for PHP'.
He lists some of the features of the driver (Microsoft-supported, both thread and non-thread safe releases, a team surrounding its development and a manual/blog/forum for active participation) and the one-line call you'll need to get it up and running on your installation.