tree_test.php

<?php
    class Node
    {
        public $data;

        public $left;

        public $right;

        public $nextRight;
    }

    function newNode($data)
    {
        $p=new Node;
        $p->data=$data;
        $p->left=null;
        $p->right=null;
        $p->nextRight=null;
    }

    function connect( &$p )
    {
        $p->nextRight=null;

        recursion ( $p );
    }

    function recursion ( &$p )
    {
        // Base case
        if (!$p)
            return;

        // Set the nextRight pointer for p's left child
        if ($p->left)
            $p->left->nextRight = $p->right;

        // Set the nextRight pointer for p's right child
        // p->nextRight will be NULL if p is the right most child at its level
        if ($p->right)
            $p->right->nextRight = ($p->nextRight)? $p->nextRight->left: NULL;

        // Set nextRight for other nodes in pre order fashion
        recursion ($p->left);
        recursion ($p->right);    
    }

    $root= new Node;
    $root->data=10;
    $root->left=newNode(8);
    $root->right=newNode(2);
    $root->left->left=newNode(3);
    
    connect($root);
    
    var_dump($root);