Question

我的数据库（mysql）中有一个具有下一个模式的表：

-----------------------------
- id  name         parent_id
-----------------------------
- 1   grandfather  NULL
- 2   father       1
- 3   uncle        1
- 4   son          2
- 5   brother      2
- 6   sister       2

我想通过以下方式在页面上显示它：

grandfather 
father
son
brother
sister
Uncle

（预遍历）

这是我遇到的最好的解决方案（不起作用）

$sql = "SELECT p1.id, p1.name, p1.parent_id FROM tree p1 ORDER BY p1.id";
$result = $conn->query($sql);

while($row = mysqli_fetch_assoc($result)) {
        arbol($row, $result);
};
function arbol($fila, $result) {
            echo $fila["name"] . "<br>";
            $flag = false;
            while($busqueda = mysqli_fetch_row($result)) {
                if($busqueda[2]==$fila["id"]){
                    $flag = true;
                    break;
                }
            };

            if ($flag){
                foreach ($result as $ruta) {
                    if($ruta["parent_id"]==$fila["id"]){
                        arbol($ruta, $result);
                    };
                };


            } else {
                return;
            }
        };
    };

结果是，我第一次遍历到底部，但没有遍历其余树：

Grandfather
parent
son

我做错了什么？或您对我有什么建议？

注意：完成此操作后，我将有许多“祖父”，这就是为什么会出现while的原因（我会在其中添加“ parent_id = NULL”条件）。

编辑：执行此操作后，行的结构：

while( $row = mysqli_fetch_assoc( $result)){
    $resguard[] = $row;
}
print_r($resguard);

是这个（为清楚起见而格式化）：

Array ( 
[0] => Array ( [id] => 1 [name] => Grandfather [parent_id] => ) 
[1] => Array ( [id] => 2 [name] => Parent [parent_id] => 1 ) 
[2] => Array ( [id] => 3 [name] => Uncle [parent_id] => 1 ) 
[3] => Array ( [id] => 4 [name] => Son [parent_id] => 2 ) 
[4] => Array ( [id] => 5 [name] => Brother [parent_id] => 2 ) 
[5] => Array ( [id] => 6 [name] => Sister [parent_id] => 2 ) 
)

Answer 1

这是一个适用于您的数据集的示例，并假定原始数据按ID排序（就像您的查询一样）。我相信要走的路是编写将较小的函数转换为树并逐步遍历的小函数。可能有可能在数组中进行遍历并在您执行操作时以一次跳跃的方式将其打印出来，但是我的大脑目前无法想到一种好方法。

function make_tree($data) {
    $tree = [];

    foreach ($data as $node) {
        insert($tree, $node);
    }

    return $tree;
}

function insert(&$root, &$node) {
    if (!$root) {
        $root = $node;
    }
    else if ($root["id"] === $node["parent_id"]) {
        $root["children"][] = $node;
    }
    else if (array_key_exists("children", $root)) {
        foreach ($root["children"] as &$c) {
            if (insert($c, $node)) {
                break;
            }
        }
    }
}

function preorder(&$root) {
    if ($root) {
        yield $root;

        if (array_key_exists("children", $root)) {
            foreach ($root["children"] as $c) {
                yield from preorder($c);
            }
        }
    }
}

$data = [
    ["id" => 1, "name" => "Grandfather", "parent_id" => null],
    ["id" => 2, "name" => "Father", "parent_id" => 1],
    ["id" => 3, "name" => "Uncle", "parent_id" => 1],
    ["id" => 4, "name" => "Son", "parent_id" => 2],
    ["id" => 5, "name" => "Brother", "parent_id" => 2],
    ["id" => 6, "name" => "Sister", "parent_id" => 2]
];

$tree = make_tree($data);

foreach (preorder($tree) as $node) {
    echo $node["name"]."\n";
}

输出：

Grandfather
Father
Son
Brother
Sister
Uncle

这里是repl。

用php显示存储在数据库中的家谱树

1 个答案: