PHP 数组按值分组的函数和最佳实践

array_group_by(array $array, mixed $key_or_callback, bool $preserve_keys = false): array

$fruits = [
    ['name' => 'Apple', 'type' => 'Red'],
    ['name' => 'Banana', 'type' => 'Yellow'],
    ['name' => 'Orange', 'type' => 'Orange'],
    ['name' => 'Mango', 'type' => 'Yellow'],
];

$grouped_by_type = array_group_by($fruits, 'type');

// 输出按类型分组后的数组
print_r($grouped_by_type);

Array
(
    [Red] => Array
    (
        [0] => Array
        (
            [name] => Apple
            [type] => Red
        )
    )
    [Yellow] => Array
    (
        [0] => Array
        (
            [name] => Banana
            [type] => Yellow
        )
        [1] => Array
        (
            [name] => Mango
            [type] => Yellow
        )
    )
    [Orange] => Array
    (
        [0] => Array
        (
            [name] => Orange
            [type] => Orange
        )
    )
)

function group_by(array $array, string $key): array
{
    $result = [];
    foreach ($array as $item) {
        $result[$item[$key]][] = $item;
    }
    return $result;
}

$grouped_by_type_and_name = array_reduce($fruits, function($result, $item) {
    $result[$item['type']][$item['name']] = $item;
    return $result;
}, []);

$grouped_by_name = array_column($fruits, null, 'name');