I always start with arrays for quick prototyping then I jump back to objects for storing the same data. Not only because I suspected it would be faster (because of the class definition) but because the data I'm sharing with has their own methods that knows how to deal with that data. Here is an example that I moved array structures into their own class, the code is much nicer and it runs a bit faster if you measure a few million times.
Interesting article that confirms my theory :D, thanks for writing it.
Nice! Yeah, the ability to encapsulate behavior is one of the most obvious benefits of a class but there's been a general belief in PHP for years that doing so was more expensive than doing it "manually". That may have been true once, but it's definitely not true today. In fact quite the opposite.