PHP递归调用如何改成长尾递归？

本文共计464个文字，预计阅读时间需要2分钟。

这是一个地名，JSON格式，需要转换成数组或对象形式。

json[ {id: 9, address: 上海, parent_id: 0}, {id: 1, address: 安徽, parent_id: 0}, {id: 2, address: 江苏, parent_id: 0}, {id: 3, address: 合肥, parent_id: 0}]

这是一个地名，json格式，需要转换成数组或对象形式

$json='[ {"id":9,"address":"上海","parent_id":0}, {"id":1,"address":"安徽","parent_id":0}, {"id":2,"address":"江苏","parent_id":0}, {"id":3,"address":"合肥","parent_id":1}, {"id":4,"address":"庐阳区","parent_id":3}, {"id":5,"address":"大杨镇","parent_id":4}, {"id":6,"address":"南京","parent_id":2}, {"id":7,"address":"玄武区","parent_id":6}, {"id":8,"address":"梅园新村街道","parent_id":7}, {"id":16,"address":"梅园新村小区","parent_id":8}, {"id":17,"address":"蔷薇园","parent_id":16}, {"id":18,"address":"三号楼","parent_id":17}, {"id":10,"address":"黄浦区","parent_id":9}, {"id":11,"address":"外滩","parent_id":10}, {"id":12,"address":"安庆","parent_id":1}, {"id":13,"address":"浙江","parent_id":0}, {"id":14,"address":"嘉兴","parent_id":13}, {"id":15,"address":"河南","parent_id":0} ]'; 这是字符串格式，需要转换成数组，转换成数组的语句如下

//首先这是字符串，需要转换成数组才能被调用 $json = json_decode($json,true); //打印下看看是不是数组，如果是，才能对其进行调研 print_r($json); 下面就用到，递归循环调用

//定义一个函数城市树，里面传递参数 function City_tree($json,$id,$step){ //静态调用方法 static $tree=[]; //遍历出数组中的值 foreach ($json as $key => $value){ //数组的key值必须与id值相同 if($value['parent_id']==$id){ //添加拼接字符-- $flg=str_repeat('--',$step); $value['address']=$flg.$value['address']; $tree[] = $value; //执行循环 City_tree($json,$value['id'],$step+1); } } return $tree; } $tree = City_tree($json,0,0); foreach ($tree as $value1){ echo $value1['address'].'
'; } 最后实现的，结果为：

上海 --黄浦区 ----外滩 安徽 --合肥 ----庐阳区 ------大杨镇 --安庆 江苏 --南京 ----玄武区 ------梅园新村街道 --------梅园新村小区 ----------蔷薇园 ------------三号楼 浙江 --嘉兴 河南