用php从mysql数据库构建多维数组

Question

我有一个理论上的问题，我似乎搞不懂。假设我在数据库中有以下数据：

Main    Sub1   Sub2
a       x      y
x       t      u
u       f      g

我想在PHP/mYSQL中创建一个多维数组，实际上是问“每个'main‘组件是由什么组成的？”

结果会是这样的：

Array
   (
   [0] => a
     (
     [0] => x
       (
       [0] => t
       [1] => u
       )
         (
         [0] => f
         [1] => g
         )
     [1] => y
     )
   )

我的努力产生了许多数组，而不是多维数组。

Answer 1

你可以使用引用来解决这个问题，尽管结果会变得有点混乱：

$res = [];

foreach ($rows as $row) {
    // check if we have each sub component
    if (!isset($res[$row['sub1']])) {
        $res[$row['sub1']] = $row['sub1'];
    }
    if (!isset($res[$row['sub2']])) {
        $res[$row['sub2']] = $row['sub2'];
    }
    // build new component with references to the sub components
    $res[$row['main']] = [&$res[$row['sub1']], &$res[$row['sub2']]];
}

print_r($res);

输出

Array
(
    [x] => Array
        (
            [0] => t
            [1] => Array
                (
                    [0] => f
                    [1] => g
                )

        )

    [y] => y
    [a] => Array
        (
            [0] => Array
                (
                    [0] => t
                    [1] => Array
                        (
                            [0] => f
                            [1] => g
                        )

                )

            [1] => y
        )

    [t] => t
    [u] => Array
        (
            [0] => f
            [1] => g
        )

    [f] => f
    [g] => g
)

您可以通过仅过滤出数组来清理结果：

print_r(array_filter($res, 'is_array'));

输出

Array
(
    [x] => Array
        (
            [0] => t
            [1] => Array
                (
                    [0] => f
                    [1] => g
                )

        )

    [a] => Array
        (
            [0] => Array
                (
                    [0] => t
                    [1] => Array
                        (
                            [0] => f
                            [1] => g
                        )

                )

            [1] => y
        )

    [u] => Array
        (
            [0] => f
            [1] => g
        )

)