Quoting http://php.net/manual/en/intro.mssql.php:
The MSSQL extension is not available anymore on Windows with PHP 5.3 or later. SQLSRV, an alternative driver for MS SQL is available from Microsoft: » http://msdn.microsoft.com/en-us/sqlserver/ff657782.aspx.
Once you downloaded that, follow the instructions at this page:
In a nutshell:
Put the driver file in your PHP extension directory.
Modify the php.ini file to include the driver. For example:extension=php_sqlsrv_53_nts_vc9.dllRestart the Web server.
See Also (copied from that page)
The PHP Manual for the SQLSRV extension is located at http://php.net/manual/en/sqlsrv.installation.php and offers the following for Installation:
The SQLSRV extension is enabled by adding appropriate DLL file to your PHP extension directory and the corresponding entry to the php.ini file. The SQLSRV download comes with several driver files. Which driver file you use will depend on 3 factors: the PHP version you are using, whether you are using thread-safe or non-thread-safe PHP, and whether your PHP installation was compiled with the VC6 or VC9 compiler. For example, if you are running PHP 5.3, you are using non-thread-safe PHP, and your PHP installation was compiled with the VC9 compiler, you should use the php_sqlsrv_53_nts_vc9.dll file. (You should use a non-thread-safe version compiled with the VC9 compiler if you are using IIS as your web server). If you are running PHP 5.2, you are using thread-safe PHP, and your PHP installation was compiled with the VC6 compiler, you should use the php_sqlsrv_52_ts_vc6.dll file.
The drivers can also be used with PDO.