php中使用redis实现秒杀

<?php
/**
 * $producttotal 商品总数
 * $productsellnum 已售商品数量
 * $currentbuynum 当前购买数量
 */

//商品总数
$producttotal = 100;

//当前购买数量
$currentbuynum = 5;

try {
    $redis = new redis();
    $result = $redis->connect('127.0.0.1',6379);
    if(!$result){
        throw new exception('redis连接失败');
    }
} catch (exception $e){
    echo $e->getmessage();
    die;
}

//监视 product_sell_num
$redis->watch('product_sell_num');
//已售商品数量
$productsellnum = $redis->get('product_sell_num');
//判断商品是否剩余
if($productsellnum + $currentbuynum <= $producttotal){
    $redis->multi();
    $redis->set('product_sell_num',$productsellnum + $currentbuynum);
    $status = $redis->exec();
    if($status){
        //对购买信息处理
    }else{
        return "抢购失败";
    }
}else{
    return "抢购结束";
}