<?php/*class ListNode{ var $val; var $next = NULL; function __construct($x){  $this->val = $x; }}*/function Merge($pHead1, $pHead2){ if($pHead1 == NULL)  return $pHead2; if($pHead2 == NULL)  return $pHead1; $reHead = new ListNode(); if($pHead1->val < $pHead2->val){  $reHead = $pHead1;  $pHead1 = $pHead1->next; }else{  $reHead = $pHead2;  $pHead2 = $pHead2->next; } $p = $reHead; while($pHead1&&$pHead2){  if($pHead1->val <= $pHead2->val){   $p->next = $pHead1;   $pHead1 = $pHead1->next;   $p = $p->next;  }  else{   $p->next = $pHead2;   $pHead2 = $pHead2->next;   $p = $p->next;  } } if($pHead1 != NULL){  $p->next = $pHead1; } if($pHead2 != NULL)  $p->next = $pHead2; return $reHead;}