PHP从尾到头打印链表实例讲解

//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;}