<?php
$prize_arr = array(
    '0' => array('id' => 1, 'title' => '二等奖', 'v' => 20),
    '1' => array('id' => 2, 'title' => '三等奖', 'v' => 100),
    '2' => array('id' => 3, 'title' => '四等奖', 'v' => 100),
    '3' => array('id' => 4, 'title' => '未中奖', 'v' => 1000),
);
  
foreach ($prize_arr as $key => $val) {
    $arr[$val['id']] = $val['v'];
}
 //$arr= [1=>'phone',2=>'note']
 //print_r($arr);die;
$prize_id = getRand($arr); //根据概率获取奖品id
$data['msg'] = ($prize_id == 4) ? 0 : 1; //如果为0则没中 
$data['prize_title'] = $prize_arr[$prize_id - 1]['title']; //中奖奖品
echo json_encode($data);
exit; //以json数组返回给前端
  
function getRand($proArr) { //计算中奖概率
    $rs = ''; //z中奖结果
    $proSum = array_sum($proArr); //概率数组的总概率精度
    //概率数组循环
    foreach ($proArr as $key => $proCur) {
        $randNum = mt_rand(1, $proSum);
        if ($randNum <= $proCur) {
            $rs = $key;
            break;
        } else {
            $proSum -= $proCur;
        }
    }
    unset($proArr);
    return $rs;
}









?>