php下载远程文件(支持断点续传)的实现代码

<?php 
/**
 * 远程下载 断点续传
 * by http://www.jbxue.com
*/
    class httpdownload  
    {  
      var $data = null;  
      var $data_len = 0;  
      var $data_mod = 0;  
      var $data_type = 0;  
      var $data_section = 0; //section download  
      var $sentSize=0;  
      var $handler = array('auth' => null);  
      var $use_resume = true;  
      var $use_autoexit = false;  
      var $use_auth = false;  
      var $filename = null;  
      var $mime = null;  
      var $bufsize = 2048;  
      var $seek_start = 0;  
      var $seek_end = -1;  
      var $totalsizeref = 0;  
      var $bandwidth = 0;  
      var $speed = 0; 
     
    /*
     *初始化一些下载参数
     */   
    function initialize()  
    {  
        global $HTTP_SERVER_VARS;  
        if (!$this->use_auth) //use authentication  
        {  
              if ($this->_auth()) //no authentication  
              {  
                      header('WWW-Authenticate: Basic realm="Please enter your username and password"');  
                      header('HTTP/1.0 401 Unauthorized');  
                      header('status: 401 Unauthorized');  
                      if ($this->use_autoexit) exit();  
                      return false;  
              }  
        }  
        if ($this->mime == null) $this->mime = "application/octet-stream"; //default mime 
         
        //如果设置了range 
        if (isset($_SERVER['HTTP_RANGE']) || isset($HTTP_SERVER_VARS['HTTP_RANGE']))  
        {  
            if (isset($HTTP_SERVER_VARS['HTTP_RANGE'])) $seek_range = substr($HTTP_SERVER_VARS['HTTP_RANGE'] , strlen('bytes='));  
            else $seek_range = substr($_SERVER['HTTP_RANGE'] , strlen('bytes='));//for example:Range:  bytes=0-100 
            $range = explode('-',$seek_range); //explode seek_range to range array 
             
            //处理开始字节与结束字节 
            if ($range[0] > 0) {  
                  $this->seek_start = intval($range[0]);  
            }  
            if ($range[1] > 0) $this->seek_end = intval($range[1]);  
            else $this->seek_end = -1; 
             
            if (!$this->use_resume)  
            {  
                  $this->seek_start = 0;  
                  //header("HTTP/1.0 404 Bad Request");  
                  //header("Status: 400 Bad Request");  
                  //exit;  
                  //return false;  
            } else {  
                  $this->data_section = 1;  
            }  
        } else { 
                /*
                Range头域可以请求实体的一个或者多个子范围，Range的值为0表示第一个字节，也就是Range计算字节数是从0开始的
                表示头500个字节：bytes=0-499
                表示第二个500字节：bytes=500-999
                表示最后500个字节：bytes=-500
                表示500字节以后的范围：bytes=500-
                第一个和最后一个字节：bytes=0-0,-1
                同时指定几个范围：bytes=500-600,601-999
                */ 
            $this->seek_start = 0;//第一个字节  
            $this->seek_end = -1; //最后一个字节 
        }  
        $this->sentSize=0;  
        return true; 
    } 
     
    /*
     *配置请求头
     */ 
    function header($size,$seek_start=null,$seek_end=null) {  
          header('Content-type: ' . $this->mime); //类型 
          header('Content-Disposition: attachment; filename="' . $this->filename . '"'); //文件名 
          header('Last-Modified: ' . date('D, d M Y H:i:s \G\M\T' , $this->data_mod)); //修改时间 
           
          //断点续传 
          if ($this->data_section && $this->use_resume) {  
                header("HTTP/1.0 206 Partial Content");  
                header("Status: 206 Partial Content");  
                header('Accept-Ranges: bytes');  
                header("Content-Range: bytes $seek_start-$seek_end/$size");  
                header("Content-Length: " . ($seek_end - $seek_start + 1));  
          } else { //重新下载 
                header("Content-Length: $size");  
          } 
    } 
    function download_ex($size) {  
          if (!$this->initialize()) return false;  
          ignore_user_abort(true);  
          //Use seek end here  
          if ($this->seek_start > ($size - 1)) $this->seek_start = 0;  
          if ($this->seek_end <= 0) $this->seek_end = $size - 1;  
           
          $seek = $this->seek_start; 
          $this->header($size,$seek,$this->seek_end);  
          $this->data_mod = time();  
          return true; 
    } 
    function download() {  
        if (!$this->initialize()) return false;  
        try {  
                $seek = $this->seek_start;  
                $speed = $this->speed;  
                $bufsize = $this->bufsize;  
                $packet = 1;  
                //do some clean up  
                @ob_end_clean();  
                $old_status = ignore_user_abort(true);  
                @set_time_limit(0);  
                $this->bandwidth = 0;  
                $size = $this->data_len;  
                if ($this->data_type == 0) //download from a file  
                {  
                    $size = filesize($this->data);  
                    if ($seek > ($size - 1)) $seek = 0;  
                    if ($this->filename == null) $this->filename = basename($this->data);  
                    $res = fopen($this->data,'rb');//以二进制读模式打开文件  
                    if ($seek) fseek($res , $seek);//定位文件中设置文件指针位置  
                    if ($this->seek_end < $seek) $this->seek_end = $size - 1;  
                    $this->header($size,$seek,$this->seek_end); //always use the last seek  
                    $size = $this->seek_end - $seek + 1;  
                    while (!(connection_aborted() || connection_status() == 1) && $size > 0)  
                    {  
                        if ($size < $bufsize) {//如果剩下的尚未下载的文件size小于bufsize，就一次下载完  
                            echo fread($res , $size);  
                            $this->bandwidth += $size;  
                            $this->sentSize+=$size;  
                        } else {  
                            echo fread($res , $bufsize);  
                            $this->bandwidth += $bufsize;  
                            $this->sentSize+=$bufsize;  
                        }  
                        $size -= $bufsize; //扣除已经下载好的size 
                        flush(); //刷新缓冲 实现echo动态输出 
                        //限制下载速度 
                        if ($speed > 0 && ($this->bandwidth > $speed*$packet*1024)) {  
                            sleep(1);  
                            $packet++;  
                        }  
                    }  
                    fclose($res);  
                }  
                elseif ($this->data_type == 1) //download from a string  
                {  
                    if ($seek > ($size - 1)) $seek = 0;  
                    if ($this->seek_end < $seek) $this->seek_end = $this->data_len - 1;  
                    $this->data = substr($this->data , $seek , $this->seek_end - $seek + 1);  
                    if ($this->filename == null) $this->filename = time();  
                    $size = strlen($this->data);  
                    $this->header($this->data_len,$seek,$this->seek_end);  
                    while (!connection_aborted() && $size > 0) {  
                          if ($size < $bufsize) {  
                                $this->bandwidth += $size;  
                                $this->sentSize+=$size;  
                          } else {  
                                $this->bandwidth += $bufsize;  
                                $this->sentSize+=$bufsize;  
                          }  
                          echo substr($this->data , 0 , $bufsize);  
                          $this->data = substr($this->data , $bufsize);  
                          $size -= $bufsize;  
                          flush();  
                          if ($speed > 0 && ($this->bandwidth > $speed*$packet*1024)) {  
                                sleep(1);  
                                $packet++;  
                          }  
                    }  
                } else if ($this->data_type == 2) {  
                    //just send a redirect header  
                    header('location: ' . $this->data);  
                }  
                if($this->totalsizeref==$this->sentSize ) echo "end download\n";//error_log("end download\n", 3,"/usr/local/www/apache22/LOGS/apache22_php.err");  
                else echo "download is canceled\n";//error_log("download is canceled\n", 3,"/usr/local/www/apache22/LOGS/apache22_php.err");  
                if ($this->use_autoexit) exit();  
                //restore old status  
                ignore_user_abort($old_status);  
                set_time_limit(ini_get("max_execution_time"));  
            } 
            catch(Exception $e) {  
                  //error_log("cancel download\n".$e, 3,"/usr/local/www/apache22/LOGS/apache22_php.err"); 
                  echo "cancel download\n".$e; 
            }  
          return true; 
    } 
    function set_byfile($dir) {  
          if (is_readable($dir) && is_file($dir)) {  
                $this->data_len = 0;  
                $this->data = $dir;  
                $this->data_type = 0;  
                $this->data_mod = filemtime($dir);  
                $this->totalsizeref = filesize($dir);  
                return true;  
          } else return false; 
    } 
    function set_bydata($data) {  
          if ($data == '') return false;  
                $this->data = $data;  
                $this->data_len = strlen($data);  
                $this->data_type = 1;  
                $this->data_mod = time();  
                return true; 
    } 
    function set_byurl($data) {  
          $this->data = $data;  
          $this->data_len = 0;  
          $this->data_type = 2;  
          return true; 
    } 
    function set_lastmodtime($time) {  
          $time = intval($time);  
          if ($time <= 0) $time = time();  
          $this->data_mod = $time; 
    } 
    function _auth() {  
          if (!isset($_SERVER['PHP_AUTH_USER'])) return false;  
          if (isset($this->handler['auth']) && function_exists($this->handler['auth'])) {  
                return $this->handler['auth']('auth' , $_SERVER['PHP_AUTH_USER'],$_SERVER['PHP_AUTH_PW']);  
          }  
          else return true; //you must use a handler  
    } 
    } 
     
    //usage 
    $object = new httpdownload(); 
    $object->speed = 512;//限速512kb/秒 
    $object->set_byurl("http://localhost/cooldock.rar");//服务器文件名,包括路径 
    $object->filename = "test.rar";//下载另存为的文件名 
    $object->download(); 
?>