原理是使用hash随机字符串，位数不足时用0补齐，同时把函数后出现的字母按英文字母表进行数字替换。

再根据hash出来的长度换算成对应的百分比占比，用于获取对应区间内的奖品。

该算法只适用于轮播抽奖活动，并不适用于转盘抽奖JS，转盘的抽奖需要自行修改成360°圆形区间占比即可。

function random($length=16, $type=4) {
    switch ($type) {
        case 1: $str = '0123456789'; $num = 9; break;
        case 2: $str = 'a0sqd1fwg2hej3krl4ztx5cyv6bun7mi8o9p'; $num = 35; break;
        case 3: $str = 'A0SQD1FWG2HEJ3KRL4ZTX5CYV6BUN7MI8O9P'; $num = 35; break;
        case 4: $str = 'qAw0eSrQrtDt1yFyWuGi2oHpEaJs3dKfRgLh4jZkTlXz5xCcYvVb6nBmUN7MI8O9P'; $num = 64; break;
        default:
            return false;
        break;
    }
    $ret = '';
    for ($i=0; $i < $length; $i++) {
        $ret .= $str[mt_rand(0, $num)];
    }
    return $ret;
}
function get_hash($id){
    $max = 6;
    $str = bin2hex($id);
    $hash = substr($str, 0, 6);
    if (strlen($hash)<6){
        $hash = str_pad($hash, 6, "0");
    }
    $alphabet = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'];
    $alphabet = array_flip($alphabet);
    for ($i=0; $i<$max; $i++) {
        if (is_numeric($hash{$i}) == false) {
            $hash{$i} = $alphabet[$hash{$i}];
        }
    }
    return $hash;
}
$rand = get_hash(random());
$array = [
    [
        'min' => '0.0001',
        'max' => '0.1',
        'title' => '中了只鸡',
    ],
    [
        'min' => '0.1',
        'max' => '1',
        'title' => '吃饭了没',
    ],
    [
        'min' => '1',
        'max' => '20',
        'title' => '三等奖',
    ],
    [
        'min' => '20',
        'max' => '50',
        'title' => '二等奖',
    ],
    [
        'min' => '50',
        'max' => '100',
        'title' => '别想了没一等奖',
    ],
];
$ratio = 100 / 1000000;
$num = $ratio*$rand;
foreach ($array as $value) {
    // TM中奖了啊
    if ($num > $value['min'] && $num <= $value['max']) {
        var_dump($rand);
        var_dump($num);
        var_dump($value['title']);
        break;
    }
}