Microsoft has released a driver for php to connect to MS SQL server. There where already ways if doing this but now there is a new kid on the block written by Microsoft itself.
The SQL Server Driver for PHP Community Technology Preview (CTP) is designed to enable reliable, scalable integration with SQL Server for PHP applications deployed on the Windows platform. The Driver for PHP is a PHP 5 extension that allows the reading and writing of SQL Server data from within PHP scripts. It provides a procedural interface for accessing data in all Editions of SQL Server 2005 and SQL Server 2000 (including Express Edition), and makes use of PHP features, including PHP streams to read and write large objects.
MSDN channel 9 is running a video interview with some of the developers which you can view here below. You can find out more about the driver itself here
removed the embedded video because wmv embedding is not working for all platforms and browser equally right. You can view the video via this link