Microsoft recently released SQL Server Drivers for PHP 2.0 which adds support for PDO with a new PDO_SQLSRV and contains bug fixes for the existing SQLSRV driver. The native APIs present in the PHP Driver for SQL Server 1.1 are still present, there is additional support for the PDO API.
Download the SQL Server Driver 2.0 for PHPMicrosoft says “In order to support the new PDO_SQLSRV driver to be consistent with the existing SQLSRV driver, the code was re-architected into a core functional layer and an "API" layer above. The SQLSRV driver is built from this re-architected code, and also includes some important bug fixes. This release is available to all SQL Server users at no additional charge.”
The Drivers for PHP for SQL Server are used for connecting PHP applications to Microsoft SQL Server.