We are really excited about the progress of PHP 5.3 release.  This is a milestone release for PHP on Windows as libraries are being brought up to date, PHP Core developers can use the Visual Studio 9 compiler and performance will be greatly improved.

Unfortunately, the current SQL Server Driver for PHP v1.0 does not support PHP 5.3 and will cause IIS to crash.  You will end up seeing something like this.

HTTP Error 500.0 - Internal Server Error

C:\php\php-cgi.exe - The FastCGI process exited unexpectedly

Followed by a Microsoft Windows error box.

CGI / FastCGI stopped working and was closed.

The dev team responsible for the SQL Server Driver for PHP is hard at work on v1.1 which will support PHP 5.3.  Please add their blog to your favorite RSS reader http://blogs.msdn.com/sqlphp.