Binary Tree: Manage hierarchic trees of objects

This class can be used to manage an hierarchies of objects within a binary.

Each object of the class is a node that may have a reference two descendent objects: the right and the left nodes.

Each tree node object may contain a data variable of an arbitrary type.

The class provides functions for adding nodes given the left and right descendent nodes (oif any), as well to traverse the tree and print the data value of the nodes and count the number of nodes in the tree. (PHP5)