Php 将数组中的值指定为键，并合并同一键的记录

我在PHP中有如下数组（Codeigniter）。我想用国家名称将它们分组。所以国家密钥的值将成为外部数组的密钥

Array
(
    [0] => Array
        (
            [city] => Buenos Aires
            [country] => Argentina
        )

    [1] => Array
        (
            [city] => Adelaide
            [country] => Australia
        )

    [2] => Array
        (
            [city] => Brisbane
            [country] => Australia
        )

    [3] => Array
        (
            [city] => Fremantle
            [country] => Australia
        )

    [4] => Array
        (
            [city] => Melbourne
            [country] => Australia
        )

    [5] => Array
        (
            [city] => Sydney
            [country] => Australia
        )

)

我想把它转换成数组，如下所示，这样国家将成为关键的城市名单根据国家的名称

Array
(
    [Argentina] => Array
    (
        [0] => Buenos Aires
    )

    [Australia] => Array
    (
        [0] => Adelaide
        [1] => Brisbane
        [2] => Melbourne
        [3] => Sydney
    )

)

这是密码

$arr = [//your arr];

$result = []; // will be your output

foreach($arr as $k => $v){
   $result[$v['country']][] = $v['city'];
}

---

我希望这能起作用

先显示一些代码。@u\u mulder。。我在for循环中尝试了很多东西，但没有达到预期的效果欢迎！如果这个解决方案解决了你的问题，请接受我的回答。