<?php abstract class Node { /*--------------------------- This class provides basic functionality common to nodes. Every node has an id and a parent. ---------------------------*/ protected $id; protected $parent; function Node() { // dummy constructor } final function getID() { return $this->id; } final function getParent() { return $this->parent; } final function setID($id) { $this->id = $id; } final function setParent($p) { $this->parent = $p; } } ?>