在php中从数组构建"交叉表"或"数据透视表"

<?php
// 原始数组
$data = [
    ['name' => 'Alice', 'age' => 25, 'gender' => 'female'],
    ['name' => 'Bob', 'age' => 30, 'gender' => 'male'],
    ['name' => 'Charlie', 'age' => 35, 'gender' => 'male'],
    ['name' => 'David', 'age' => 40, 'gender' => 'male'],
];

// 获取行和列
$rows = array_unique(array_column($data, 'age'));
$cols = array_unique(array_column($data, 'gender'));

// 初始化交叉表
$cross_table = [];
foreach ($rows as $row) {
    $cross_table[$row] = [];
    foreach ($cols as $col) {
        $cross_table[$row][$col] = 0;
    }
}

// 填充交叉表
foreach ($data as $item) {
    $cross_table[$item['age']][$item['gender']]++;
}

// 输出交叉表
print_r($cross_table);
?>

Array
(
    [25] => Array
        (
            [female] => 1
            [male] => 0
        )

    [30] => Array
        (
            [female] => 0
            [male] => 1
        )

    [35] => Array
        (
            [female] => 0
            [male] => 1
        )

    [40] => Array
        (
            [female] => 0
            [male] => 1
        )
)