Cory Fowler has a recent post explaining how you can enable one of the most recent PHP releases (PHP 5.4) on your Windows Azure website via the " Bring-Your-Own-Runtime" feature.

Much like many other developers, I like to live on the bleeding edge, learning new language features, using the latest tools so naturally one of the things I wanted to see in Windows Azure Web Sites is support for PHP 5.4. I’m pleased to be telling you today in this post that support for Bring-Your-Own-Runtime is now available in Windows Azure Web Sites. Out of the box, Windows Azure Web Sites supports PHP 5.3 as you can see from the snapshot of the portal below. In this article I’ll explain how to enable PHP 5.4 in Windows Azure Web Sites.

You'll need to set up and configure an Azure instance to work with (if you don't already have one) and navigate to its management Dashboard once complete. You can then setup a handler mapping that points to an uploaded version of the PHP Windows binary for 5.4 on your document root. Then all that's left is to upload (via FTP or git) this executable and you'll be all set.