随机抽取值

普通写法

function get_chance($chance = [
    '和谐' => 3000,
    '爱国' => 5000,
    '敬业' => 110,
    '友善' => 1000,
    '富强' => 3000,
])
{
    $cardRange = [];
    $num = rand(0, array_sum(array_values($chance)));
    $total = 0;
    foreach ($chance as $key => $value) {
        $totalBefore = $total;
        $total += $value;
        if ($num >= $totalBefore && $num < $total) {
            return $key;
        }
        $cardRange[$key] = [$totalBefore, $total];
    }
    return $key;
}

在swoole环境中的写法, 兼容所有环境

function get_chance($chance = [
    '和谐' => 3000,
    '爱国' => 5000,
    '敬业' => 110,
    '友善' => 1000,
    '富强' => 3000,
])
{
    // 在协程中避免rand一段时间内值一致的问题
    $cardRange = [];
    $total = array_sum(array_values($chance));
    // $randValue = substr(explode(' ', microtime())[0], 0, 8);
    $randValue = strrev(substr(explode(' ', microtime())[0], 2, 6)) / 1000000;
    $rangeBefore = 0;
    $total2 = 0;
    foreach ($chance as $key => $value) {
        $total2 += $value;
        $rangeAfter = $total2 / $total;
        if ($randValue >= $rangeBefore && $randValue < $rangeAfter) {
            return $key;
        }
        $rangeBefore = $rangeAfter;
    }
    return $key;
}

校验数据和预期值的差异量

$t = [
    '记' => 300,
    '得' => 900,
    '我' => 150,
];
$r = [
    '记' => 0,
    '得' => 0,
    '我' => 0,
];
for ($k = 0; $k <= 10000; $k++) {
    $r[get_chance($t)]++;
}
var_dump($r);