The SQL Server Driver for PHP...

...is designed to enable reliable, scalable integration with SQL Server for PHP applications deployed on the Windows platform. Read Introduction to the SQL Server Driver for PHP Get it Beginner's Guide Learn more Forum

SQL Server Driver for PHP Highlights

Microsoft Drivers for PHP for SQL Server
The Microsoft Drivers 3.0 for SQL Server for PHP are PHP 5 extensions that allows for the reading and writing of SQL Server data from within PHP scripts. Please visit the following page to download the latest release: http://www.microsoft.com/download/en/details.aspx?id=20098

Source code now available
The SQL Server Driver for PHP allows PHP developers to access SQL Server databases. The SQL Server Driver for PHP relies on the Microsoft SQL Server ODBC Driver to handle the low-level communication with SQL Server.
Microsoft has published the source code to the driver on this site. You can download the source code and provide feedback in the form of bug reports and feature requests.