利用PHP怎么对链表进行打印

//递归版本
function printListFromTailToHead($head)
{
  if($head == NULL){
    return [];
  }

  $arr = array();
  $cur = $head;

  if($cur->next != null){
    $arr = printListFromTailToHead($cur->next);  
  }
  array_push($arr, $cur->val);
  return $arr;



}
//非递归版本
function printListFromTailToHead($head)
{
  if($head == NULL){
    return [];
  }

  $cur = $head;
  $arr = array();
  $re = array();

  while($cur != NULL){
    array_push($arr, $cur->val);
    $cur = $cur ->next;
  }


  while(!empty($arr)){
    $tmp = array_pop($arr);
    array_push($re, $tmp);
  }
  return $re;
}