In a new post to his site Benjamin Eberlei continues his look at using various platform-as-a-service (PaaS) offerings for PHP available today and talks about using Composer with Windows Azure via its post deployment hooks.
It turns out that Azure Websites - to support other platforms that require compiling - actually has an extremly robust deployment system (as far as I understood its internals). If Composer fails during this step, the website will still be served from the currently running version and you don't have to face unexpected downtime. To actually run Composer as a post-deployment tool you have to do some manual work.
This manual work comes in the form of a special ".deployment" file included in the root of your repository that defines the command to execute (a custom script). Included there at the end of the post is the PHP code you'll need to put in this custom script to get the latest version of composer and then require the phar file for use later in your application.