Transform the tree structure into array in PHP (flatten the tree structure and keep the sorting of upper and lower levels)

Preface

Doing it php In the function of transforming tree structure into array, sometimes it is necessary to directly flatten the tree structure and arrange it from top to bottom in the order of tree structure , At this time, another method is needed .

terms of settlement

// Tree structure data to array （ Flatten tree structure , Keep superior and subordinate sorting ）
function treeToList($arr, $pid = 0)
{
    
    $array = array();
    foreach ($arr as $val) {
    
        $inData = array(
            "key" => $val["key"],
            "p_key" => $pid,
            "title" => $val["title"],
        );
        $array[] = $inData;
        if (isset($val["children"])) {
    
            $children = treeToList($val["children"], $val["key"]);
            if ($children) {
    
                $array = array_merge($array, $children);
            }
        }
    }
    return $array;
}

Directly flatten the tree structure , Keep sorting up and down .

$tree = [
    [
        "key" => 1,
        "p_key" => 0,
        "title" => " Hubei province ",
        "children" => [
            [
                "key" => 2,
                "p_key" => 1,
                "title" => " Wuhan City ",
                "children" => [
                    [
                        "key" => 3,
                        "p_key" => 2,
                        "title" => " Wuchang District ",
                        "children" => [
                            [
                                "key" => 4,
                                "p_key" => 3,
                                "title" => " Sheshan Xishan pote 1 Number ",
                                "children" => [
                                    [
                                        "key" => 5,
                                        "p_key" => 4,
                                        "title" => " Yellow Crane Tower ",
                                    ],
                                ],
                            ],
                        ],
                    ],
                ],
            ],
        ],
    ],
];

$data = [
    [
        "key" => 1,
        "p_key" => 0,
        "title" => " Hubei province ",
    ],
    [
        "key" => 2,
        "p_key" => 1,
        "title" => " Wuhan City ",
    ],
    [
        "key" => 3,
        "p_key" => 2,
        "title" => " Wuchang District ",
    ],
    [
        "key" => 4,
        "p_key" => 3,
        "title" => " Sheshan Xishan pote 1 Number ",
    ],
    [
        "key" => 5,
        "p_key" => 4,
        "title" => " Yellow Crane Tower ",
    ],
];