PHP游戏概率方法

<?php

 function createRandomKey($randArr, $rateKey){
        $total = 0;
        $chooseArr = array();
        $pow = 0;　　　　　
        //比如array( array('id' => 1, 'rate' => 40.99), array('id' => 2, 'rate' => 59.01));
       /* foreach($randArr as $k => $v){　　　　　　
            $tmp = explode('.', strval($v[$rateKey]));
            if($tmp[1] && strlen($tmp[1]) > $pow){
                $pow = strlen($tmp[1]);
            }
        }*/
        $r = pow(10, $pow);
        foreach($randArr as $key => $value){
            $total = $total + $value[$rateKey] * $r;
            $chooseArr[$key] = $total;
        };
        $rand = rand(1, $total);
        $bofore = 0;
        foreach ($chooseArr as $k => $v){
            $v = $v * $r;
            if($rand > $bofore && $rand <= $v){
               $chooseIndex = $k;
                break;
            }
            $bofore = $v;
        }
        return $chooseIndex;
    }

    $randArr = [
            0 => ['point' => 15,'rate' => 0],
            1 => ['point' => 5,'rate' => 0],
            2 => ['point' => 10,'rate' => 0],
            3 => ['point' => 11,'rate' => 0],
            4 => ['point' => 13,'rate' => 10],
            5 => ['point' => 20,'rate' => 80],
            6 => ['point' => 50,'rate' => 0],
            7 => ['point' => 80,'rate' => 0],
            8 => ['point' => 10,'rate' => 0],
            9 => ['point' => 60,'rate' => 10],

        ];

    $a = createRandomKey($randArr,$rate = 'rate');
    var_dump($a);
    var_dump($randArr[$a]['point']);