php编写的抽奖程序中奖概率算法

function get_rand($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;
}

$prize_arr = array(
'0' => array('id'=>1,'prize'=>'平板电脑','v'=>1),
'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'=>'10Q币','v'=>22),
'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'];
}
 
$rid = get_rand($arr); //根据概率获取奖项id
 
$res['yes'] = $prize_arr[$rid-1]['prize']; //中奖项
unset($prize_arr[$rid-1]); //将中奖项从数组中剔除，剩下未中奖项
shuffle($prize_arr); //打乱数组顺序
for($i=0;$i<count($prize_arr);$i++){
$pr[] = $prize_arr[$i]['prize'];
}
$res['no'] = $pr;
echo json_encode($res);

/**
* 抽奖
* @param int $total
*/
function getReward($total=1000)
{
$win1 = floor((0.12*$total)/100);
$win2 = floor((3*$total)/100);
$win3 = floor((12*$total)/100);
$other = $total-$win1-$win2-$win3;
$return = array();
for ($i=0;$i<$win1;$i++)
{
$return[] = 1;
}
for ($j=0;$j<$win2;$j++)
{
$return[] = 2;
}
for ($m=0;$m<$win3;$m++)
{
$return[] = 3;
}
for ($n=0;$n<$other;$n++)
{
$return[] = '谢谢惠顾';
}
shuffle($return);
return $return[array_rand($return)];
}
$data = getReward();
echo $data;
?>