PHP - 循环遍历数组并仅在迭代之间发生变化时才打印出值

Question

如果有人问过这个问题，但我找不到满足我需求的解决方案，我深表歉意。

我在 PHP 7 应用程序中有一个数组，如下所示：

$data = [

    0 => [

        'regulations_label' => 'Europe',

        'groups_label' => 'G1',

        'filters_label' => 'FF1'

    ],

    1 => [

        'regulations_label' => 'Europe',

        'groups_label' => 'G1',

        'filters_label' => 'FF900'

    ],

    2 => [

        'regulations_label' => 'Europe',

        'groups_label' => 'G1',

        'filters_label' => 'FF324234'

    ],

    3 => [

        'regulations_label' => 'Europe',

        'groups_label' => 'G2',

        'filters_label' => 'FF23942'

    ],

    4 => [

        'regulations_label' => 'America',

        'groups_label' => 'G29',

        'filters_label' => 'FF3242'

    ],

    5 => [

        'regulations_label' => 'America',

        'groups_label' => 'G29',

        'filters_label' => 'FF78978'

    ],

    6 => [

        'regulations_label' => 'America',

        'groups_label' => 'G29',

        'filters_label' => 'FF48395043'

    ],

    7 => [

        'regulations_label' => 'Asia',

        'groups_label' => 'G2000',

        'filters_label' => 'FF7'

    ],

    // ...

];

我想要实现的输出是这样的：

Europe

    - G1

        -- FF1

        -- FF900

    - G2

        -- FF23942

America

    - G29

        -- FF3242

        -- FF48395043

Asia

    - G2000

        -- FF7

本质上，它所做的就是以结构化格式输出数组，以便它显示regulations_label后跟任何对应的groups_label，然后是任何filters_label。

遍历整个数组很简单，例如

foreach ($data as $d) {

    echo $d['regulations_label'] . "\n";

    echo ' - ' . $d['groups_label'] . "\n";

    echo ' -- ' . $d['filters_label'] . "\n";

}

然而，这引入了“重复”标题regulations_label，groups_label因为它正在打印每个键。但是我不知道如何检查这在foreach语句期间是否已更改，因为$d它始终是当前元素。

我试图根据以前的数组键进行检查：

foreach ($data as $key => $d) {

   if ($data[$key-1]['regulations_label'] !== $d['regulations_label']) {

       echo $d['regulations_label'] . "\n";

       echo "-" . $d['groups_label'] . "\n";

   }

}

麻烦的是，这然后只打印 1groups_label所以我最终会得到 - 例如：

Europe

- G1

America

...

它不会达到“G2”。

我不禁觉得我在用一种奇怪的方式来处理这个问题。谁能建议一个更好的解决方案？

Answer 1

您可以使用foreach通过使用组regulations_label和groups_label$group = [];foreach($data as $v){  $group[$v['regulations_label']][$v['groups_label']][] = $v['filters_label'];}

Answer 2

您需要做的就是记住上次处理的内容，然后添加几个 IF$data = [    0 => ['regulations_label' => 'Europe','groups_label' => 'G1','filters_label' => 'FF1'],    1 => ['regulations_label' => 'Europe','groups_label' => 'G1','filters_label' => 'FF900'],    2 => ['regulations_label' => 'Europe','groups_label' => 'G1','filters_label' => 'FF324234'],    3 => ['regulations_label' => 'Europe','groups_label' => 'G2','filters_label' => 'FF23942'],    4 => ['regulations_label' => 'America','groups_label' => 'G29','filters_label' => 'FF3242'],    5 => ['regulations_label' => 'America','groups_label' => 'G29','filters_label' => 'FF78978'],    6 => ['regulations_label' => 'America','groups_label' => 'G29','filters_label' => 'FF48395043'],    7 => ['regulations_label' => 'Asia','groups_label' => 'G2000','filters_label' => 'FF7']];$last_reg = NULL;$last_grp = NULL;foreach ($data as $reg) {    if ( $last_reg != $reg['regulations_label']) {        echo $reg['regulations_label'] . "\n";        $last_reg = $reg['regulations_label'];        $last_grp = NULL;        $last_filter = NULL;    }    if ( $last_grp != $reg['groups_label']) {        echo "\t - " . $reg['groups_label'] . "\n";        $last_grp = $reg['groups_label'];    }    echo "\t\t - " . $reg['filters_label'] . "\n";}结果：Europe     - G1         - FF1         - FF900         - FF324234     - G2         - FF23942America     - G29         - FF3242         - FF78978         - FF48395043Asia     - G2000         - FF7