JAVA抽奖的算概率法

$prize_arr = array(
'0' => array('id'=>1,'prize'=>'平板电脑','v'=>3),
'1' => array('id'=>2,'prize'=>'数码相机','v'=>5),
'2' => array('id'=>3,'prize'=>'音箱设备','v'=>10),
'3' => array('id'=>4,'prize'=>'4G优盘','v'=>12),
'4' => array('id'=>5,'prize'=>'Q币10元','v'=>20),
'5' => array('id'=>6,'prize'=>'下次没准就能中哦','v'=>50),
);

foreach ($prize_arr as $key => $val) {
$arr[$val['id']] = $val['v'];
}

$rid = getRand($arr); //根据概率获取奖项id
$res['msg'] = ($rid==6)?0:1; //如果为0则没中
$res['prize'] = $prize_arr[$rid-1]['prize']; //中奖项
echo json_encode($res);

//计算概率
function getRand($proArr) {
$result = '';

//概率数组的总概率精度
$proSum = array_sum($proArr);

//概率数组循环
foreach ($proArr as $key => $proCur) {
$randNum = mt_rand(1, $proSum);
if ($randNum <= $proCur) {
$result = $key;
break;
} else {
$proSum -= $proCur;
}
}
unset ($proArr);

return $result;
}