WebMatrix is a free web development tool from Microsoft that includes everything you need for web site development. WebMatrix provides an integrated environment for building, testing, and deploying web sites. This integrated environment includes an embedded IIS web server, database, and programming template that lets you get started with web site development, which includes PHP and .NET applications. If you use any of the widely used blog and content management solutions based on the PHP programming language (such as WordPress, Joomla, or Drupal) or .NET-based solutions (such as DotNetNuke), WebMatrix allows you to configure and download these applications quickly through its Open Gallery feature.
Recently, I published an article on web matrix on dzone on how to get started with developing php applications using web matrix. Checkout the the article for more details.