PHP无限级分类(一)

无限级分类在web项目中应用非常广泛，比如商品分类、权限节点、组织架构等等。
下面介绍两种将二维数组整理成无限级树形结构的方法：
数据如下：

$data = [
      ["id"=>1,"pid"=>0,"name"=>"服饰"],
      ["id"=>2,"pid"=>0,"name"=>"电子"],
      ["id"=>3,"pid"=>0,"name"=>"食品"],
      ["id"=>4,"pid"=>1,"name"=>"男装"],
      ["id"=>5,"pid"=>4,"name"=>"裤子"],
      ["id"=>6,"pid"=>2,"name"=>"电脑"],
      ["id"=>7,"pid"=>6,"name"=>"笔记本电脑"],
      ["id"=>8,"pid"=>2,"name"=>"手机"]
      
];

一.递归法：

function getTree($data, $pid = 0)
{
    $tree = [];
    foreach ($data as $k => $v)
    {
        if ($v['pid'] == $pid) 
        {
            unset($data[$k]);
            $v['child'] = getTree($data, $v['id']);
            $tree[] = $v;
        }
    }
    return $tree;
}
$tree = getTree($data);

二.引用法(效率更高)：

function getTree($data){
    $list=[];
    foreach ($data as $v){
        $id=$v['id'];
        $list[$id]=$v;
    }
    $tree=[];
    foreach ($list as $k=>$v){
        $pid=$v['pid'];
        if(isset($list[$pid])){
            $list[$pid]['child'][]=&$list[$k];
        }else{
            $tree[$v['id']]=&$list[$k];
        }
    }
    return $tree;
}
$tree = getTree($data);

输出(JSON)如下：

[
    {
        "id": 1,
        "pid": 0,
        "name": "服饰",
        "child": [
            {
                "id": 4,
                "pid": 1,
                "name": "男装",
                "child": [
                    {
                        "id": 5,
                        "pid": 4,
                        "name": "裤子",
                        "child": []
                    }
                ]
            }
        ]
    },
    {
        "id": 2,
        "pid": 0,
        "name": "电子",
        "child": [
            {
                "id": 6,
                "pid": 2,
                "name": "电脑",
                "child": [
                    {
                        "id": 7,
                        "pid": 6,
                        "name": "笔记本电脑",
                        "child": []
                    }
                ]
            },
            {
                "id": 8,
                "pid": 2,
                "name": "手机",
                "child": []
            }
        ]
    },
    {
        "id": 3,
        "pid": 0,
        "name": "食品",
        "child": []
    }
]