将数组中的值指定为键并合并相同键的记录

Question

我在PHP（Codeigniter）中有如下所示的数组。我想使用国家/地区名称对它们进行分组。所以country键的值将成为外部数组的关键

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
        )

)

我想将其转换为如下所示的数组，因此国家/地区将成为按照国家/地区名称列入城市列表的关键

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

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

)

Answer 1

这是代码，

$arr = [//your arr];

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

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

我希望这会起作用