PHP如何按关联键值对多维数组进行分组

function groupBy($array, $key) {
    return array_reduce($array, function($result, $item) use ($key) {
        $groupKey = $item[$key];
        if (!array_key_exists($groupKey, $result)) {
            $result[$groupKey] = [];
        }
        $result[$groupKey][] = $item;
        return $result;
    }, []);
}

// 示例数据
$students = [
    ['name' => 'Alice', 'grade' => 'A'],
    ['name' => 'Bob', 'grade' => 'B'],
    ['name' => 'Charlie', 'grade' => 'A'],
    ['name' => 'David', 'grade' => 'C'],
    ['name' => 'Eve', 'grade' => 'B'],
];

// 按照成绩进行分组
$groupedStudents = groupBy($students, 'grade');

// 输出结果
print_r($groupedStudents);

Array
(
    [A] => Array
        (
            [0] => Array
                (
                    [name] => Alice
                    [grade] => A
                )

            [1] => Array
                (
                    [name] => Charlie
                    [grade] => A
                )

        )

    [B] => Array
        (
            [0] => Array
                (
                    [name] => Bob
                    [grade] => B
                )

            [1] => Array
                (
                    [name] => Eve
                    [grade] => B
                )

        )

    [C] => Array
        (
            [0] => Array
                (
                    [name] => David
                    [grade] => C
                )

        )

)