I haven't tried it, but according to MSDN, the following link contains the driver that PHP requires to connect to SQL Server:

http://msdn.microsoft.com/en-us/sqlserver/cc299381.aspx

You will need to modify your PHP.ini file to get this to work.

As far as IIS, what version are you running?

Thanks Donald, I reader the same page, but it seems not updated in the last two year :) I think we'll use xampp for apache + php.

I discovered through trying to set this up myself on a Win7/IIS/PHP/MSSQL stack that there is not an official sqlsrv driver for PHP 5.5 or above. Only for PHP 5.4 or 5.3. I ended up using an unofficial version I found after various searching and it seems to work fine, obvious caveat is it's not an 'official' MS version.

If your are interested I found the drivers here - https://social.msdn.microsoft.com/Forums/sqlserver/en-US/e1d37219-88a3-46b2-a421-73bfa33fe433/unofficial-php-55-drivers-x86

Another option would be to use PHP5.4 in your production environment and the official sqlsrv drivers from MS.

Or just use MySQL in xampp. I don't have that option myself as I am using an existing MSSQL db.