PHP写的资源下载防盗链类分享

这几天在写一个php防盗链外部资源下载处理函数，昨天晚上刚完成编写，中间遇到了些问题，这里就不详述了；
以下是自写的简单的php防盗链处理类(重新整理编写成类文件，以便后期改进)；

<?php
/**
 *
 * 防盗链外部资源下载处理类
 *
 * @link   http://jb51.net
 *
 */
class burglardow{
 /**
     * 初始许可下载状态
     * @var    allow
     * @access private
     */
 private $allow      =  false;
 /**
     * 初始下载地址
     * @var    dowurl
     * @access private
     */
 private $dowurl     =  null;
 /**
     * 初始来路域名
     * @var    remoteurl
     * @access private
     */
 private $remoteurl  =  null;
 /**
     * 初始许可资源取用域名列表
     * @var    allowurl
     * @access private
     */
 private $allowurl   =  array();
 /**
     * 初始转跳地址
     * @var    location
     * @access private
     */
 private $location   =  null;

 public function __construct($dowurl,$location,array $allowurl){
  // 初始下载地址
  $this->dowurl   = $dowurl;
  // 初始许可资源取用域名列表
  $this->allowurl = $allowurl;
  // 初始转跳地址
  $this->location = $location;

  $this->remoteurl = @parse_url($_server['http_referer']);                                                      // 获取来路域名
  if(!is_array($this->remoteurl))
   header("http/1.1 301 moved permanently");
   header("location: ".$this->location);

  if(isset($this->remoteurl['host'])){
   if(in_array($this->remoteurl['host'],$this->allowurl)){                                                   // 判断是否来至许可域名
    $this->allow  = true;                                                                                 // 下载许可状态为：真
   }
  }
  unset($this->allowurl,$this->remoteurl);                                                                      // 释放内存变量
 }

 /**
  * 防盗链资源下载
  * @access public
  * @return mixed
  */
 public function dow(){
  $fileinfo = get_headers($this->dowurl,1);                                                                     // 获取远程文件头部信息

  if(true === $this->allow){                                                                                    // 判断是否许可下载资源
   //判断配置文件是否存在
   if(is_file('config.ini')){
    $filecon = parse_ini_file('config.ini');
   }else{
    $filename   =  basename($fileinfo['content-location']);
    $fileconstr = "filename  = {$filename}\r\nfileurl   = {$fileinfo['content-location']}\r\nfilesize   = {$fileinfo['content-length']}";
    $handle = fopen ('config.ini', "wb");                                                                 // config.ini文件不存在则创建文件
    if (fwrite ($handle, $fileconstr) == false) {                                                         // 数据写入文件
     echo "file creation failed ...";
    }
    fclose ($handle);                                                                                     // 关闭一个已打开的文件指针
    $filecon = parse_ini_file('config.ini');
   }
   if(!empty($$this->dowurl)){
    $fp = @fopen($$this->dowurl, "rb");                                                                   // 二进制模式读取文件
    if (!$fp)
      exit("download a mistake.\n\n");

    // 输出远程资源
    header("content-type:text/html;charset=utf-8");
    header('content-description: file transfer');
    header('content-type: application/octet-stream');
    header('content-disposition: attachment; filename='.$filecon['filename']);
    header("accept-ranges: bytes");
    header('content-transfer-encoding: binary');
    header('expires: 0');
    header('cache-control:must-revalidate,post-check=0,pre-check=0');
    header('pragma: public');
    header('content-length: '.$filecon['filesize']);
    while (!feof($fp)){
     set_time_limit(0);                                                                                 // 设置文件最长执行时间
     echo fread($fp, 1024);                                                                             // 输出文件
     flush();                                                                                           // 输出缓冲
     ob_flush();                                                                                        // 输出缓冲区中的内容
    }
    fclose($fp);
   }else{
    header("http/1.1 404 not found");
   }
  }else{
   header("http/1.1 301 moved permanently");
   header("location: ".$this->location);
  }
 }
}
// 远程资源地址
$dowurl = 'http://dldir1.qq.com/qqfile/qq/qq5.1/10055/qq5.1.exe';
// 转跳地址
$location = 'http://jb51.net';
// 许可来路域名列表
$allowurl = array(
 'jb51.net',
);
$burglardow = new burglardow($dowurl,$location,$allowurl);
$burglardow -> dow();