For MS SQL connections from php, we use
a driver provided by Microsoft. We are using version 1.1 of the driver, and it can be used to connect to MS SQL 2005 and 2008 databases (sorry, it is not compatible with SQL 2000).
Sample php code can be found in
this Knowledge Base article.
Article ID: 756, Created On: 1/21/2010, Modified: 1/21/2010