In a lot of cases arrays are used in PHP to store object-like information, like the results of a database query. I do this a lot too, but I kind of want to change things around to make use of VO's. I feel this makes a lot more sense, since most of the application I build are heavy OOP anyway, and I get all the added OOP benefits, like type-hinting, inheritance.. well, you know the deal.
In his tests he creates an array of data, a value block of three "properties", looped 1000 times) and a block of three actual properties on an object. Between each, he's using the XDebug memory usage functions to check to see which uses less resources.
Overall, there's really not that much of a difference between using either of them. So, basically, it's up to you which storage method is the simplest for you to use.