在PHP中按权重生成随机结果？

$weights = array(
    'A' => 10,
    'B' => 20,
    'C' => 30,
    'D' => 40
);

$total_weight = array_sum($weights);

$random_number = mt_rand(1, $total_weight);

$result = null;
$sum = 0;
foreach ($weights as $key => $weight) {
    $sum += $weight;
    if ($random_number <= $sum) {
        $result = $key;
        break;
    }
}