linkedListSum.php

<?php

class Node {

  public $value;
  public $next;
  public function __construct($val) {
    $this->value = $val;
  }

}

class NodeSum {
  public function sum($node1, $node2) {
    $arr1 = [];
    $arr2 = [];

    while ($node1) {
      $arr1[] = $node1->value;
      $node1 = $node1->next;
    }

    while ($node2) {
      $arr2[] = $node2->value;
      $node2 = $node2->next;
    }

    $max_len = max(count($arr1), count($arr2));
    $arr3 = [];
    $remainder = 0;
    for ($i=0;$i<$max_len;$i++) {
      $val1 = isset($arr1[$i]) ? $arr1[$i] : 0;
      $val2 = isset($arr2[$i]) ? $arr2[$i] : 0;
      $sum = $val1 + $val2 + $remainder;
      $remainder = $sum < 10 ? 0 : 1;
      $arr3[] = $sum >= 10 ? $sum - 10 : $sum;
      if ($i === $max_len - 1 && $remainder > 0) {
        $arr3[] = $remainder;
      }
    }

    $newNode = new Node($arr3[0]);
    $newMax = count($arr3);
    for ($i=1;$i<$newMax;$i++) {
      $newItem = new Node($arr3[$i]);
      $newItem->next = $newNode;
      $newNode = $newItem;
    }

    return $newNode;
  }

}

$val1 = new Node(5);
$val1->next = new Node(6);
$val1->next->next = new Node(3);

$val2 = new Node(8);
$val2->next = new Node(4);
$val2->next->next = new Node(2);

$sum = new NodeSum();
$sumNode = $sum->sum($val1, $val2);
while ($sumNode) {
  print $sumNode->value;
  $sumNode = $sumNode->next;
}

echo "\n";

$val1 = new Node(7);
$val1->next = new Node(5);
$val1->next->next = new Node(9);
$val1->next->next->next = new Node(4);
$val1->next->next->next->next = new Node(6);

$val2 = new Node(8);
$val2->next = new Node(4);

$sum = new NodeSum();
$sumNode = $sum->sum($val1, $val2);
while ($sumNode) {
  print $sumNode->value;
  $sumNode = $sumNode->next;
}