We've just shipped the released version for the SQL Server 2005 Driver extensions for PHP 5 - if you're running the CTP version make sure you update to this version.
I think the coolest thing that comes with this download is the Help file (.chm) that is part of the package and has an insane amount of detail on how to use it and how it actually works.
to get it working just drop your files into your PHP extension directory - and is based on your chosen distribution of php - make sure you add it into your php.ini as well.v
php_sqlsrv.dll <-- non thread safe
go get it, and tell me how it worked for you!