Sum of leaf node in BST using recursion in php

Php program for Sum of leaf node in BST using recursion. Here more solutions.

<?php
// Php program for
// Sum of all leaf nodes of binary search tree
// Using recusion
class TreeNode
{
	public $data;
	public $left;
	public $right;
	public	function __construct($data)
	{
		$this->data = $data;
		$this->left = NULL;
		$this->right = NULL;
	}
}
class BinarySearchTree
{
	public $root;
	public	function __construct()
	{
		$this->root = NULL;
	}
	// insert a new node
	public	function addNode($data)
	{
		// Create a new node
		$node = new TreeNode($data);
		if ($this->root == NULL)
		{
			// When adds a first node in bst
			$this->root = $node;
		}
		else
		{
			$find = $this->root;
			// Add new node to proper position
			while ($find != NULL)
			{
				if ($find->data >= $data)
				{
					if ($find->left == NULL)
					{
						// When left child empty
						// So add new node here
						$find->left = $node;
						return;
					}
					else
					{
						// Otherwise
						// Visit left sub-tree
						$find = $find->left;
					}
				}
				else
				{
					if ($find->right == NULL)
					{
						// When right child empty
						// So add new node here
						$find->right = $node;
						return;
					}
					else
					{
						// Visit right sub-tree
						$find = $find->right;
					}
				}
			}
		}
	}
	// Sum of leaf nodes
	public	function leafNodeSum($node)
	{
		if ($node != NULL)
		{
			if ($node->left == NULL && $node->right == NULL)
			{
				// When node is leaf node
				return $node->data;
			}
			// Visit to left and right subtree
			return $this->leafNodeSum($node->left) + 
              $this->leafNodeSum($node->right);
		}
		return 0;
	}
	public static function main()
	{
		$tree = new BinarySearchTree();
		// Add nodes in binary search tree
		/*
		            5
		          /   \ 
		         /     \
		        3       9
		       / \     /  \
		      2   4   8    10
		             / 
		            6

		*/
		$tree->addNode(5);
		$tree->addNode(3);
		$tree->addNode(9);
		$tree->addNode(2);
		$tree->addNode(4);
		$tree->addNode(8);
		$tree->addNode(10);
		$tree->addNode(6);
		// Test
		printf("%d", $tree->leafNodeSum($tree->root));
	}
}
BinarySearchTree::main();

Output

22