Engine Yard/Orchestra, a PHP platform-as-a-service (PaaS) provider has announced the release of PHP 5.4 as a part of their cloud offerings:

We’re pleased to announce the general availability of PHP 5.4 for Orchestra PHP Cloud. We are committed to keeping your apps running on the latest and greatest version of PHP. After careful lab testing, we’ll upgrade your apps as newer versions of PHP become available. What if you’re still using PHP 5.3? Don’t worry, Orchestra PHP Cloud will continue to maintain its PHP 5.3 stack. You will be able to choose which version of PHP you would like to use when you launch a new app.

The default when you set up a new application will now be PHP 5.4, so be sure you're paying attention on setup if you need something else. You can find out more about the Orchestra PaaS on the Engine Yard site and try it out for free to see how your app performs.