<?php
$total = 100;
$num = 10;
$min = "0.01";    //每个人最少得0.01元
for ($i=1;$i<$num;$i++){
    $safe_total = ($total-($num-$i)*$min);    //随机安全上限
    $safe_total = $safe_total/getIntNum(1,$num-$i);    //公正随机处理(更好的算法可以放到这里处理)
    $money = getIntNum($min,$safe_total);
    $total = round($total-$money,2);
    $new[$i] = $money;
    echo '第'.$i.'个红包：'.$money.' 元，余额：'.$total.' 元 <br/>';
}
function getIntNum($min,$max){
    return round(mt_rand($min*100,$max*100),2)/100;
}
if($num==1) {
    $money = $total;
} else {
    $key = array_rand($new,1);
    $money = $new[$key];
}
//随机发一个红包
var_dump($money);