php--防止DDos攻击代码

<?php
//查询禁止IP
$ip =$_SERVER['REMOTE_ADDR'];
$fileht=".htaccess2";
if(!file_exists($fileht))file_put_contents($fileht,"");
$filehtarr=@file($fileht);
if(in_array($ip."\r\n",$filehtarr))die("Warning:"."<br>"."Your IP address are forbided by some reason, IF you have any question Pls emill to [e-mail]!");

//加入禁止IP
$time=time();
$fileforbid="log/forbidchk.dat";
if(file_exists($fileforbid))
{ if($time-filemtime($fileforbid)>60)unlink($fileforbid);
else{
    $fileforbidarr=@file($fileforbid);
    if($ip==substr($fileforbidarr[0],0,strlen($ip)))
    {
        if($time-substr($fileforbidarr[1],0,strlen($time))>600)unlink($fileforbid);
        elseif($fileforbidarr[2]>600){file_put_contents($fileht,$ip."\r\n",FILE_APPEND);unlink($fileforbid);}
        else{$fileforbidarr[2]++;file_put_contents($fileforbid,$fileforbidarr);}
    }
}
}
//防刷新
$str="";
$file="log/ipdate.dat";
if(!file_exists("log")&&!is_dir("log"))mkdir("log",0777);
if(!file_exists($file))file_put_contents($file,"");
$allowTime = 120;//防刷新时间
$allowNum=10;//防刷新次数
$uri=$_SERVER['REQUEST_URI'];
$checkip=md5($ip);
$checkuri=md5($uri);
$yesno=true;
$ipdate=@file($file);
foreach($ipdate as $k=>$v)
{ $iptem=substr($v,0,32);
    $uritem=substr($v,32,32);
    $timetem=substr($v,64,10);
    $numtem=substr($v,74);
    if($time-$timetem<$allowTime){
        if($iptem!=$checkip)$str.=$v;
        else{
            $yesno=false;
            if($uritem!=$checkuri)$str.=$iptem.$checkuri.$time."1\r\n";
            elseif($numtem<$allowNum)$str.=$iptem.$uritem.$timetem.($numtem+1)."\r\n";
            else
            {
                if(!file_exists($fileforbid)){$addforbidarr=array($ip."\r\n",time()."\r\n",1);file_put_contents($fileforbid,$addforbidarr);}
                file_put_contents("log/forbided_ip.log",$ip."--".date("Y-m-d H:i:s",time())."--".$uri."\r\n",FILE_APPEND);
                $timepass=$timetem+$allowTime-$time;
                die("Warning:"."<br>"."Sorry,you are forbided by refreshing frequently too much, Pls wait for ".$timepass." seconds to continue!");
            }
        }
    }
}
if($yesno) $str.=$checkip.$checkuri.$time."1\r\n";
file_put_contents($file,$str);
?>