PHP抽奖程序概率算法

//概率算法,6个奖项
$prize_arr = array(
'0' => array('id'=>1,'prize'=>'iphone6','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'=>'50Q币','v'=>24),
'4' => array('id'=>5,'prize'=>'10Q币','v'=>60),
'5' => array('id'=>6,'prize'=>'1Q币','v'=>1900),
);

//每个奖品的中奖几率,奖品ID作为数组下标
foreach($prize_arr as $val){
$item[$val['id']] = $val['v'];
}

function get($item){
//中奖概率基数
$num = array_sum($item);//当前一等奖概率1/2000

foreach($item as $k=>$v){
//获取一个1到当前基数范围的随机数
$rand = mt_rand(1,$num);
if($rand <= $v){
//假设当前奖项$k=2,$v<=5才能中奖
$res = $k;
break;
}else{
//假设当前奖项$k=6,$v>1900,则没中六等奖,总获奖基数2000-1900,前五次循环都没中则2000-1-5-10-24-60=1900,必中6等奖,哈哈
$num -= $v;
}
}
return $res;
}

$res = get($item);
$h = $prize_arr[$res-1]['prize'];
echo $h.'; ';