php中使用redis實現秒殺

<?php
/**
 * $productTotal 商品總數
 * $productSellNum 已售商品數量
 * $currentBuyNum 當前購買數量
 */

//商品總數
$productTotal = 100;

//當前購買數量
$currentBuyNum = 5;

try {
    $redis = new redis();
    $result = $redis->connect('127.0.0.1',6379);
    if(!$result){
        throw new Exception('redis連接失敗');
    }
} catch (Exception $e){
    echo $e->getMessage();
    die;
}

//監視 product_sell_num
$redis->watch('product_sell_num');
//已售商品數量
$productSellNum = $redis->get('product_sell_num');
//判斷商品是否剩餘
if($productSellNum + $currentBuyNum <= $productTotal){
    $redis->multi();
    $redis->set('product_sell_num',$productSellNum + $currentBuyNum);
    $status = $redis->exec();
    if($status){
        //對購買信息處理
    }else{
        return "搶購失敗";
    }
}else{
    return "搶購結束";
}