以下为引用的内容：

$object = new httpdownload();

$object->set_byfile($file)%N#H#%;//服务器文件名,包括路径

$object->filename = $filename;//下载另存为的文件名

$object->download();

3.源文件:

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;

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

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='));

$range = explode('-',$seek_range);

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 {

$this->seek_start = 0;

$this->seek_end = -1;

}

$this->sentSize=0;

return true;

}

function header($size,$seek_start=null,$seek_end=null) {

header('Content-type: ' . $this->mime);

header('Content-Disposition: attachment; filename="' . $this->filename . '"');

header('Last-Modified: ' . date('D, d M Y H:i:s \G\M\T' , $this->data_mod));

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 {

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;

$this->header($size,$seek,$this->seek_end);

$this->data_mod = time();

return true;

}

function download() {

if (!$this->initialize()) return false;

try {

error_log("begin download\n", 3,"/usr/local/www/apache22/LOGS/apache22_php.err");

$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');

if ($seek) fseek($res , $seek);

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) {

echo fread($res , $size);

$this->bandwidth += $size;

$this->sentSize+=$size;

} else {

echo fread($res , $bufsize);

$this->bandwidth += $bufsize;

$this->sentSize+=$bufsize;

}

$size -= $bufsize;

flush();

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 )error_log("end download\n", 3,"/usr/local/www/apache22/LOGS/apache22_php.err");

else 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");

}

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

}

}

?>