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.'; ';