Binary tree in PHP

gistfile1.php

<?php
class TreeNode
{
	public $value;
	public $left;
	public $right;

	public function __construct($value)
	{
		$this->value = $value;
		$this->left = null;
		$this->right = null;
	}
}

class Tree
{
	private $root;

	public function contains($v){
		return $this->_contains($this->root, $v);
	}

	private function _contains($node, $v)
	{
		if ($node === null) return false;
		if ($node->value === $v) return true;
		return $v < $node->value ? $this->_contains($node->left, $v) : $this->_contains($node->right, $v);
	}

	public function replace(TreeNode $parent, TreeNode $oldNode, TreeNode $newNode)
	{
		if ($parent === null) $this->root = $newNode;

		if ($parent->left === $oldNode) {
			$parent->left = $newNode;
		} elseif ($parent->right === $oldNode) {
			$parent->right = $newNode;
		} else {
			throw new Exception();
		}
	}

	public function insert($v)
	{
		if ($this->root === null) {
			$this->root = new TreeNode($v);
			return $this;
		}

		$node = $this->root;
		while (true) {
			if ($v <= $node->value) {
				if ($node->left === null) {
					$node->left = new TreeNode($v);
					return $this;
				}
				$node = $node->left;
			} else {
				if ($node->right === null) {
					$node->right = new TreeNode($v);
					return $this;
				}
				$node = $node->right;
			}
		}
	}
}



$t = new Tree();
$t->insert(1)->insert(2);
var_dump($t->contains(2));

thanks for your effort