dotcloud seems about as close a match as you could get, including the PaaS pricing which seems expensive to people who are comfortable setting up their own server. I have seen Heroku working for PHP but it needs a certain type of application that doesn't need to write files and uses postgres. WordPress can actually live within these requirements, with a plugin that rewrites mysql queries as postgres, but it isn't easy.

There are more options if all you need is WordPress. ZippyKid and page.ly both seem to be high quality and economical.