It really depends on how you write PHP. If you write Object Oriented PHP and use a framework with strong OOP principals you probably will have no problem learn

It really depends on how you write PHP. If you write Object Oriented PHP and use a framework with strong OOP principals you probably will have no problem learning Rails. If you've used MVC before, and you understand the role of a Model, View, Controller, data bindings, ORM, etc. then you should have no problem learning Rails. If all you know is PHP and it's control structures, and you expect your file to be interpreted every time you visit a URL, then you will probably have more difficultly learning Rails. It would be helpful to know what you love about PHP.