lottery.php

 



  $v){
        $rand_num_max += $v['rate'];
    }
    
    // 初始化随机数，奖品区间
    $rand_num = mt_rand(1, $rand_num_max);
    $left_interval = 0;
    $right_interval = 0;
    $last_right_interval = 0;
    
    foreach($arr_prize as $k => $v){
        // 左区间
        $left_interval = $last_right_interval;
        // 右区间
        $right_interval = $left_interval + $v['rate'];
        // 上一个右区间
        $last_right_interval = $right_interval;        
        // 判断随机数是否落在对应的区间
        if($left_interval < $rand_num && $rand_num <= $right_interval){
            return $k;
        }
    }
}

// 总概率精度是100，这样比较好计算概率是否正常
$arr_prize = array( 
    array('id' => 1, 'name' => '一等奖', 'rate' => 1), 
    array('id' => 2, 'name' => '二等奖', 'rate' => 5), 
    array('id' => 3, 'name' => '三等奖', 'rate' => 10), 
    array('id' => 4, 'name' => '四等奖', 'rate' => 12), 
    array('id' => 5, 'name' => '五等奖', 'rate' => 22), 
    array('id' => 6, 'name' => '不中奖', 'rate' => 50), 
);

// 中奖概率测试
$bingo_test = array(0,0,0,0,0,0);
$lottery_count = 10000;
$i = 0;

while($i++ < $lottery_count){
    $bingo_index = _get_bingo_index($arr_prize);
    $bingo_test[$bingo_index]++;
}

foreach($bingo_test as $k => $v){
    echo $arr_prize[$k]['name'] , '中奖几率：' , ($v / $lottery_count) * 100 , '%';
}

?>