php 二维数组 组装成 树形数组 使用递归方法

// 取出父类的子id集合
		function  buildTree($array,$parentId){
		        $tree = array();
		        foreach ($array as $item) {
		            if ($item['parent_id'] == $parentId) {
		                $data=$this-> buildTree($array, $item['id']);
		                if(empty($data)){
		                    $tree[]=$item['id'];
		                }else{
		                  $tree[]=$item['id'];
		                  $tree=array_merge($tree,$data);
		                }
		            }
		        }
		        return $tree;
		 }           
        $array = [
            ['id' => 1, 'parent_id' => 0, 'name' => 'Root 1'],
            ['id' => 2, 'parent_id' => 0, 'name' => 'Root 2'],
            ['id' => 3, 'parent_id' => 1, 'name' => 'Child 1'],
            ['id' => 4, 'parent_id' => 1, 'name' => 'Child 2'],
            ['id' => 5, 'parent_id' => 2, 'name' => 'Child 3'],
            ['id' => 6, 'parent_id' => 4, 'name' => 'Grandchild 1'],
        ];
        $data =buildTree($array, 1);
        var_dump($data);

// 打印是
array(3) {
  [0] => int(3)
  [1] => int(4)
  [2] => int(6)
}

// 二维数组组装成树形数组
function buildTree(array $array, $parentId = 0)
{
    $tree = array();

    foreach ($array as $item) {
        if ($item['parent_id'] == $parentId) {
            $children = buildTree($array, $item['id']);
            if ($children) {
                $item['children'] = $children;
            }
            $tree[] = $item;
        }
    }

    return $tree;
}

// 示例输入二维数组
$array = [
    ['id' => 1, 'parent_id' => 0, 'name' => 'Root 1'],
    ['id' => 2, 'parent_id' => 0, 'name' => 'Root 2'],
    ['id' => 3, 'parent_id' => 1, 'name' => 'Child 1'],
    ['id' => 4, 'parent_id' => 1, 'name' => 'Child 2'],
    ['id' => 5, 'parent_id' => 2, 'name' => 'Child 3'],
    ['id' => 6, 'parent_id' => 4, 'name' => 'Grandchild 1'],
];

$tree = buildTree($array);

// 输出树形数组
print_r($tree);

// 打印
Array
(
    [0] => Array
        (
            [id] => 1
            [parent_id] => 0
            [name] => Root 1
            [children] => Array
                (
                    [0] => Array
                        (
                            [id] => 3
                            [parent_id] => 1
                            [name] => Child 1
                        )

                    [1] => Array
                        (
                            [id] => 4
                            [parent_id] => 1
                            [name] => Child 2
                            [children] => Array
                                (
                                    [0] => Array
                                        (
                                            [id] => 6
                                            [parent_id] => 4
                                            [name] => Grandchild 1
                                        )

                                )

                        )

                )

        )

    [1] => Array
        (
            [id] => 2
            [parent_id] => 0
            [name] => Root 2
            [children] => Array
                (
                    [0] => Array
                        (
                            [id] => 5
                            [parent_id] => 2
                            [name] => Child 3
                        )

                )

        )

)