如何将树形数组，重新组合成一维数组

Question

$arr=[ 0 =>[ "id" =>"2", "cate_name" =>"外用", "parent_id" => "0", "child" => [ 0 => [ "id" => "5", "cate_name" => "外1", "parent_id" =>"2", "child" =>[ 0 => [ "id" =>"7", "cate_name" => "外外1", "parent_id" => "5", "child" => NULL ] ] ], 1=>[ "id" => "6", "cate_name" => "外2", "parent_id" => "2", "child" => NULL, ] ] ], 1 => [ "id" => "3", "cate_name" =>"内用", "parent_id" => "0", "child" => NULL, ] ] 将这个三维数组分类树，组合成这种一维数组 $arr=[ 0=>["id" =>"2","cate_name" =>"外用","parent_id" => "0",], //顶级分类 1=>["id" => "5","cate_name" => "外1","parent_id" =>"2",], //二级分类 2=>["id" =>"7","cate_name" => "外外1","parent_id" => "5",], //三级分类 3=>["id" => "6","cate_name" => "外2","parent_id" => "2",], //二级分类 4=>["id" => "3","cate_name" =>"内用","parent_id" => "0",],//顶级分类 ]; 求大神们帮忙。

Answer 1

这个没难度啊
$i=0;
foreach ($arr as $key => $value) {

if(is_array($value['child'])){
    foreach ($value['child'] as $k => $v) {
        $array[$i]['id']=$v['id'];
        $array[$i]['cate_name']=$v['cate_name'];
        $array[$i]['parent_id']=$v['parent_id'];
        $i++;
    }
}

}
var_dump($array);

Answer 2

$result = [];

function getChild($parentId, $child)
{

global $result;
foreach ($child as $item) {
   $result[] = [
        'id' =>$item['id'],
        'cate_name' => $item['cate_name'],
        'parent_id' => $parentId
    ];
    if ($item['child']) {
        getChild($item['id'], $item['child']);
    }
}

}

getChild(0, $arr);
var_dump($result);