使用ab.ext 并发测试通过
$fp = fopen("lock.txt","w+");
if(!flock($fp,LOCK_EX | LOCK_NB)){
//echo "系统繁忙，请稍后再试";
writeFile("系统繁忙，请稍后再试".flock($fp,LOCK_EX | LOCK_NB)."\n");
return;
}
writeFile("正常访问".flock($fp,LOCK_EX | LOCK_NB)."\n");
flock($fp,LOCK_UN);//释放锁
fclose($fp);
原文：https://www.cnblogs.com/zhangjian816/p/10851297.html