On his blog, Stuart Herbert has a quick tip showing how to mimic a feature of Ruby on Rails:

I'm still working on the next article in my series looking at PHP on servers, so in the mean time, check out this simple way to emulate Ruby's nice way of handling separate getter, setter and state query methods in PHP.

He admits his example isn't as elegant as the Ruby method, but it does get the job done. Code for the method is included in his post ready for cut and pasting.