PHP 5.3 for IIS is installed on a POA-managed Windows shared hosting server in accordance with the Windows Shared Hosting Deployment Guide.
The phpinfo() shows that PHP is compiled without the MS SQL support:
As Provider I want to enable the MS SQL support in PHP installed on POA-managed Windows server.
PHP on POA-managed Windows servers is installed through the POA package; actually, in backend, the POA package just unpacks and installs the stock PHP, Parallels does not modify or patch PHP installed on Windows shared hosting servers.
To enable support of MS SQL or any other missing module, Provider should download appropriate extension, place it in the PHP extensions folder (check the value of the 'extension_dir' parameter in output of the phpinfo() to find the exact location, usually it is 'C:\PHP5\ext') on the Windows server and enable it by adding the line like this in the 'php.ini' file (the exact location of the 'php.ini' file can be found in the output of the phpinfo(), usually it is 'C:\PHP5\php.ini').
As stated on the official PHP website php.net, the 'php_mssql' module is no longer shipped starting from PHP 5.3.
Provider may either find compatible 'php_mssql' module provided by 3rd-party company or try to use the 'sqlsrv' module from Microsoft.