I disagree. Rails is fantastic for quickly rolling database-driven forms apps. It includes some nice helpers for quickly integrating asynchronous behavior (Ajax), but it's certainly not mandatory. PHP5 doesn't include an OR mapper, and nor should it; an OR mapper should be part of a separate framework or library (just as it is with Ruby and Ruby on Rails). I think that Rails actually has a fairly steep learning curve. It has *very* specific ways of handling most things, and trying to fight against these things will only come back to hurt you in the end. Additionally, since it requires you to function in an MVC mode, there might be an additional bit of learning present as you figure out how to properly separate your app into presentation, model and controller layers.
At the end of the day, it all comes down to need and experience. If you know how to use PHP, why not use it? If you have to integrate a new feature into an existing Rails app, then you'd better learn Rails in a hurry. Personally, I'll build Windows server-targeted web apps in ASP.NET because I know the tooling and the backend. If I'm hosting on Linux or UNIX, I'll write it in Rails because the language and frameworks are so much nicer to use than PHP.