以下是项目代码(公众号，使用积分进行抽奖活动)，只可做参考：

public function Sncode()

{

$tid = I('request.tid', 0, 'intval'); // 大转盘id,

$wid = I('request.wid', 0, 'intval'); // 应用id,可去掉

$token = $this->getOpenId();　　　　　　 // 获取微信用户的token

// 定义数据库

$big_wheel = D('Big_wheel'); // 大转盘设置表

$big_wheel_log = M('big_wheel_log'); // 抽奖记录表

$big_code = M('big_wheel_code'); // 已抽中奖品记录表

// 查询抽奖活动数据

$where = " `id` = " . $tid;

$list = $big_wheel->relation(true)->where($where)->find();

// 查询积分，若积分不足则无法参与抽奖

$score = $this->duser['score'];

if ($score < $list['score_num']) {

echo json_encode(array('error' => 'score'));

exit;

}

//已抽奖总次数

$where_log = "`big_wheel_id`=" . $tid . " and `w_id`=" . $list['w_id'] . " and `code`='" . $token . "'";

$count = $big_wheel_log->where($where_log)->count();

//减去额外获得的抽奖机会 - 分享(此操作暂时隐藏)

$map_share['wid'] = array('eq', $wid);

$map_share['token'] = array('eq', $token);

$map_share['big_wheel_id'] = array('eq', $tid);

$count_share = M('big_wheel_share')->where($map_share)->count();

$count = $count - $count_share;

//当日限制次数

if ($list['most_num_times'] > 0) {

$where_log .= " and (addtime BETWEEN " . strtotime(date('Y-m-d 00:00:00')) . " and " . strtotime(date('Y-m-d 23:59:59')) . ")";

$count_today = $big_wheel_log->where($where_log)->count();

$count_today = $count_today - $count_share;// 当日抽奖次数减去额外获得的抽奖次数

}

//判断抽奖次数

if ($count_today >= $list['most_num_times'] && $list['most_num_times'] > 0) {

echo json_encode(array('error' => 'invalid_today', 'nums' => $list['most_num_times']));

exit;

}

// 扣除积分

M('app_dishop_duser')->where(array('id' => $this->duser['id']))->setDec('score', $list['score_num']);

//插入抽奖记录表

$data['big_wheel_id'] = $tid;

$data['w_id'] = $list['w_id'];

$data['code'] = $token;

$data['date'] = date('Y-m-d', time());

$data['addtime'] = time();

$big_wheel_log->add($data);

/*

* 奖项数组

* 是一个二维数组，记录了所有本次抽奖的奖项信息，

* 其中id表示中奖等级，prize表示奖品，v表示中奖概率。

* 注意其中的v必须为整数，你可以将对应的 奖项的v设置成0，即意味着该奖项抽中的几率是0，

* 数组中v的总和(基数)，基数越大越能体现概率的准确性。

* 本例中v的总和为100，那么中奖概率就是1%，

* 如果v的总和是10000，那中奖概率就是万分之一了。

*

*/

$prize_arr = array(

'0' => array('id' => 1, 'prize' => '1', 'v' => $list['c_probability_one']),

'1' => array('id' => 2, 'prize' => '谢谢参与', 'v' => $list['no_probability']),

'2' => array('id' => 3, 'prize' => '2', 'v' => $list['c_probability_two']),

'3' => array('id' => 4, 'prize' => '3', 'v' => $list['c_probability_three']),

);

foreach ($prize_arr as $key => $val) {

$arr[$val['id']] = $val['v'];

}

$rid = $this->get_rand($arr); //根据概率获取奖项id

$res['yes'] = $prize_arr[$rid - 1]['prize']; //中奖项

unset($prize_arr[$rid - 1]); //将中奖项从数组中剔除，剩下未中奖项

shuffle($prize_arr); //打乱数组顺序

for ($i = 0; $i < count($prize_arr); $i++) {

$pr[] = $prize_arr[$i]['prize'];

}

// 若抽中奖品，则存入库中，并返回提示

if ($res['yes'] == '1' || $res['yes'] == '2' || $res['yes'] == '3') {

//这个是保存到数据库表示你这个人抽中奖品

if ($res['yes'] == '1') {

// 查询这是第几次抽中此奖品，若抽中次数大于奖品数，则此次抽中的奖品作废

$code_count = $big_code->where(array('prizetype' => 1, 'big_wheel_id' => $tid))->count();

if ($code_count >= $list['c_num_one']) {

$data = array('prizetype' => null, 'success' => true);

echo json_encode($data);

exit;

}

$code['category'] = $list['c_name_one'];

} elseif ($res['yes'] == '2') {

// 查询这是第几次抽中此奖品，若抽中次数大于奖品数，则此次抽中的奖品作废

$code_count = $big_code->where(array('prizetype' => 2, 'big_wheel_id' => $tid))->count();

if ($code_count >= $list['c_num_two']) {

$data = array('prizetype' => null, 'success' => true);

echo json_encode($data);

exit;

}

$code['category'] = $list['c_name_two'];

} elseif ($res['yes'] == '3') {

// 查询这是第几次抽中此奖品，若抽中次数大于奖品数，则此次抽中的奖品作废

$code_count = $big_code->where(array('prizetype' => 3, 'big_wheel_id' => $tid))->count();

if ($code_count >= $list['c_num_three']) {

$data = array('prizetype' => null, 'success' => true);

echo json_encode($data);

exit;

}

$code['category'] = $list['c_name_three'];

}

$code['sn_id'] = 'sn' . time() . mt_rand(10000, 99999);

$code['w_id'] = $list['w_id'];

$code['big_wheel_id'] = $tid;

$code['prizetype'] = $res['yes'];

$code['code'] = $token;

$code['winners_time'] = time();

$code['state'] = 1;

$big_code->add($code);

$data = array('sn' => $code['sn_id'], 'prizetype' => $res['yes'], 'success' => true);

echo json_encode($data);

exit;

} else {

$data = array('prizetype' => null, 'success' => true);

echo json_encode($data);

exit;

}

}

// 抽奖概率计算

public function get_rand($proArr)

{

$result = '';

//概率数组的总概率精度

$proSum = array_sum($proArr);

//概率数组循环

foreach ($proArr as $key => $proCur) {

$randNum = mt_rand(1, $proSum);

if ($randNum <= $proCur) {

$result = $key;

break;

} else {

$proSum -= $proCur;

}

}

unset ($proArr);

return $result;

}