One important thing to note is that it has not aggregated the private elements defined in the class, which are present in the $ws object.
We will now consider the output to understand some of the side-effects and limitation of object aggregation in PHP. First, the newly created $fs and $ws objects give the expected output (according to their respective class declaration). Note that for the purposes of object aggregation, private elements of a class/object begin with an underscore character ("_"), even though there is not real distinction between public and private class/object elements in PHP.