According to this new post on the Typical Programmer blog, using getters and setters in your scripts only adds in a bit of unnecessary coupling and complexity to your scripts that you just don't need.
Today most of the popular programming languages support objects, limiting scope, modularity, passing by value, and sophisticated built-in types. There should be no reason to deliberately expose an object's data to the rest of the code because the language can enforce encapsulation and data hiding.
While not specific to PHP, the post does recommend against them because of one simple reason common to all languages that make them possible - they "break the encapsulation OOP offers". For them, they're like a cheat to get around bad coding practices and are not needed to make a successful application work.