如何在 PHP 中使用 foreach 循环来执行多维数组？ [复制]

Question

我正在从多维数组中提取数据。在使用 foreach 循环时，我很困惑，无法从数组中提取数据。这是我命名为 $result_array 的数组：

Array
(
    [0] => Array
        (
            [0] => Array
                (
                    [category_id] => 19
                    [category_name] => Food
                    [publication_status] => 1
                    [deletion_status] => 1
                )

            [1] => Array
                (
                    [category_id] => 16
                    [category_name] => Gourmet
                    [publication_status] => 1
                    [deletion_status] => 1
                )

            [2] => Array
                (
                    [category_id] => 17
                    [category_name] => Islamic Product
                    [publication_status] => 1
                    [deletion_status] => 1
                )


        )

    [1] => Array
        (
            [0] => Array
                (
                    [category_id] => 28
                    [category_name] => Dry Food
                    [publication_status] => 1
                    [deletion_status] => 1
                )

            [1] => Array
                (
                    [category_id] => 39
                    [category_name] => Testt
                    [publication_status] => 1
                    [deletion_status] => 1
                )

            [2] => Array
                (
                    [category_id] => 37
                    [category_name] => Seasonal Items
                    [publication_status] => 1
                    [deletion_status] => 1
                )

            [3] => Array
                (
                    [category_id] => 38
                    [category_name] => Icon Items
                    [publication_status] => 1
                    [deletion_status] => 1
                )

        )

    [2] => Array
        (
            [0] => Array
                (
                    [category_id] => 29
                    [category_name] => Biscuits
                    [publication_status] => 1
                    [deletion_status] => 1
                )

        )

    [3] => Array
        (
            [0] => Array
                (
                    [category_id] => 30
                    [category_name] => Nutty
                    [publication_status] => 1
                    [deletion_status] => 1
                )

        )

)

这是我的循环：

foreach($result_array as $info) {
    echo $info['category_name'].'<br>';
}

这个循环给了我一个错误，说未定义的索引category_name。我是这个领域的新手。任何人都可以启发我吗？谢谢

Answer 1

你需要双 foreach，像这样：

foreach($result_array as $outer_array)
    foreach($outer_array as $inner_array)
        echo $inner_array['category_name'] . '<br>';

Answer 2

您正在循环的$result_array 有4 个元素，它们都没有键category_name 的值。你需要加倍foreach 或更明智的做法。