php<?php
$result = array();
$configSet = array(
    6 => 0.1,
    5 => 1,
    1 => 27,
    2 => 27,
    3 => 27,
    4 => 17.9,
);
$nums = 30000000;
for($i=1;$i<$nums;$i++){
    //srand((double)microtime(true)*1000000);
    srand((double)microtime(true)*1000000);
    $random =  mt_rand(1, 1000000);
    $rand = 0;
    $thisID = 0;
    foreach($configSet as $k => $value){
        $rand += $value * 10000;
        if($random <= $rand){
            $thisID = $k;
            break;
        }
    }
    $result[$thisID] += 1;
}
foreach($result as $key => $value){
    $result[$key] = round((float)($value / $nums) * 1000000)/10000;
}
ksort($result);
print_r($result);
?>

结果是

Array
(
    [1] => 26.985
    [2] => 26.9879
    [3] => 26.987
    [4] => 17.9519
    [5] => 0.9917
    [6] => 0.0964
)

跑了很多次都是差不多的，
实际用户10000W次结果就有点问题

Array
(
    [1] => 27.0581
    [2] => 27.2639
    [3] => 27.2125
    [4] => 18.1036
    [5] => 0.3031
    [6] => 0.0588
)

怎么能保证小概率的时候波动小一点