php如何防止高并发

<?php

//优化方案4：使用非阻塞的文件排他锁

include ('./mysql.php');

//生成唯一订单号

function build_order_no(){

return date('ymd').substr(implode(NULL, array_map('ord', str_split(substr(uniqid(), 7, 13), 1))), 0, 8);

}

//记录日志

function insertLog($event,$type=0){

global $conn;

$sql="insert into ih_log(event,type)

values('$event','$type')";

mysqli_query($conn,$sql);

}

$fp = fopen("lock.txt", "w+");

if(!flock($fp,LOCK_EX | LOCK_NB)){

echo "系统繁忙，请稍后再试";

return;

}

//下单

$sql="select number from ih_store where goods_id='$goods_id' and sku_id='$sku_id'";

$rs = mysqli_query($conn,$sql);

$row = $rs->fetch_assoc();

if($row['number']>0){//库存是否大于0

//模拟下单操作

$order_sn=build_order_no();

$sql="insert into ih_order(order_sn,user_id,goods_id,sku_id,price)

values('$order_sn','$user_id','$goods_id','$sku_id','$price')";

$order_rs = mysqli_query($conn,$sql);

//库存减少

$sql="update ih_store set number=number-{$number} where sku_id='$sku_id'";

$store_rs = mysqli_query($conn,$sql);

if($store_rs){

echo '库存减少成功';

insertLog('库存减少成功');

flock($fp,LOCK_UN);//释放锁

}else{

echo '库存减少失败';

insertLog('库存减少失败');

}

}else{

echo '库存不够';

insertLog('库存不够');

}

fclose($fp);

?>