php实现大文件断点续传下载实例，看完你就知道超过100M以上的大文件如何断点传输了，这个功能还是比较经典实用的，毕竟大文件上传功能经常用得到。

require_once('download.class.php'); 
date_default_timezone_set('Asia/Shanghai'); 
error_reporting(E_STRICT); 
function errorHandler($errno, $errstr, $errfile, $errline) { 
 echo '<p>error:', $errstr, '</p>'; 
 exit(); 
} 
set_error_handler('errorHandler'); 
define('IS_DEBUG', true); 
$filePath = 'test.zip'; 
$mimeType = 'audio/x-matroska'; 
$range = isset($_SERVER['HTTP_RANGE']) ? $_SERVER['HTTP_RANGE'] : null; 
if (IS_DEBUG) { 
// $range = "bytes=1000-1999\n2000"; 
// $range = "bytes=1000-1999,2000"; 
// $range = "bytes=1000-1999,-2000"; 
// $range = "bytes=1000-1999,2000-2999"; 
} 
set_time_limit(0); 
$transfer = new Transfer($filePath, $mimeType, $range); 
if (IS_DEBUG) { 
 $transfer->setIsLog(true); 
} 
$transfer->send();

download.class.php

/** 
 * 文件传输，支持断点续传。 
 * 2g以上超大文件也有效 
 * @author MoXie 
 */ 
class Transfer { 
 /** 
  * 缓冲单元 
  */ 
 const BUFF_SIZE = 5120; // 1024 * 5 
 /** 
  * 文件地址 
  * @var <String> 
  */ 
 private $filePath; 
 /** 
  * 文件大小 
  * @var <String> Php超大数字 字符串形式描述 
  */ 
 private $fileSize; 
 /** 
  * 文件类型 
  * @var <String> 
  */ 
 private $mimeType; 
 /** 
  * 请求区域（范围） 
  * @var <String> 
  */ 
 private $range; 
 /** 
  * 是否写入日志 
  * @var <Boolean> 
  */ 
 private $isLog = false; 
 /** 
  * 
  * @param <String> $filePath 文件路径 
  * @param <String> $mimeType 文件类型 
  * @param <String> $range 请求区域（范围） 
  */ 
 function __construct($filePath, $mimeType = null, $range = null) { 
  $this->filePath = $filePath; 
  $this->fileSize = sprintf('%u', filesize($filePath)); 
  $this->mimeType = ($mimeType != null) ? $mimeType : "application/octet-stream"; // bin 
  $this->range = trim($range); 
 } 
 /** 
  * 获取文件区域 
  * @return <Map> {'start':long,'end':long} or null 
  */ 
 private function getRange() { 
  /** 
   * Range: bytes=-128 
   * Range: bytes=-128 
   * Range: bytes=28-175,382-399,510-541,644-744,977-980 
   * Range: bytes=28-175\n380 
   * type 1 
   * RANGE: bytes=1000-9999 
   * RANGE: bytes=2000-9999 
   * type 2 
   * RANGE: bytes=1000-1999 
   * RANGE: bytes=2000-2999 
   * RANGE: bytes=3000-3999 
   */ 
  if (!empty($this->range)) { 
   $range = preg_replace('/[\s|,].*/', '', $this->range); 
   $range = explode('-', substr($range, 6)); 
   if (count($range) < 2) { 
    $range[1] = $this->fileSize; // Range: bytes=-100 
   } 
   $range = array_combine(array('start', 'end'), $range); 
   if (empty($range['start'])) { 
    $range['start'] = 0; 
   } 
   if (!isset($range['end']) || empty($range['end'])) { 
    $range['end'] = $this->fileSize; 
   } 
   return $range; 
  } 
  return null; 
 } 
 /** 
  * 向客户端发送文件 
  */ 
 public function send() { 
  $fileHande = fopen($this->filePath, 'rb'); 
  if ($fileHande) { 
   // setting 
   ob_end_clean(); // clean cache 
   ob_start(); 
   ini_set('output_buffering', 'Off'); 
   ini_set('zlib.output_compression', 'Off'); 
   $magicQuotes = get_magic_quotes_gpc(); 
//   set_magic_quotes_runtime(0); 
   // init 
   $lastModified = gmdate('D, d M Y H:i:s', filemtime($this->filePath)) . ' GMT'; 
   $etag = sprintf('w/"%s:%s"', md5($lastModified), $this->fileSize); 
   $ranges = $this->getRange(); 
   // headers 
   header(sprintf('Last-Modified: %s', $lastModified)); 
   header(sprintf('ETag: %s', $etag)); 
   header(sprintf('Content-Type: %s', $this->mimeType)); 
   $disposition = 'attachment'; 
   if (strpos($this->mimeType, 'image/') !== FALSE) { 
    $disposition = 'inline'; 
   } 
   header(sprintf('Content-Disposition: %s; filename="%s"', $disposition, basename($this->filePath))); 
   if ($ranges != null) { 
    if ($this->isLog) { 
     $this->log(json_encode($ranges) . ' ' . $_SERVER['HTTP_RANGE']); 
    } 
    header('HTTP/1.1 206 Partial Content'); 
    header('Accept-Ranges: bytes'); 
    header(sprintf('Content-Length: %u', $ranges['end'] - $ranges['start'])); 
    header(sprintf('Content-Range: bytes %s-%s/%s', $ranges['start'], $ranges['end'], $this->fileSize)); 
    // 
    fseek($fileHande, sprintf('%u', $ranges['start'])); 
   } else { 
    header("HTTP/1.1 200 OK"); 
    header(sprintf('Content-Length: %s', $this->fileSize)); 
   } 
   // read file 
   $lastSize = 0; 
   while (!feof($fileHande) && !connection_aborted()) { 
    $lastSize = sprintf("%u", bcsub($this->fileSize, sprintf("%u", ftell($fileHande)))); 
    if (bccomp($lastSize, self::BUFF_SIZE) > 0) { 
     $lastSize = self::BUFF_SIZE; 
    } 
    echo fread($fileHande, $lastSize); 
    ob_flush(); 
    flush(); 
   } 
   set_magic_quotes_runtime($magicQuotes); 
   ob_end_flush(); 
  } 
  if ($fileHande != null) { 
   fclose($fileHande); 
  } 
 } 
 /** 
  * 设置记录 
  * @param <Boolean> $isLog 是否记录 
  */ 
 public function setIsLog($isLog = true) { 
  $this->isLog = $isLog; 
 } 
 /** 
  * 记录 
  * @param <String> $msg 记录信息 
  */ 
 private function log($msg) { 
  try { 
   $handle = fopen('transfer_log.txt', 'a'); 
   fwrite($handle, sprintf('%s : %s' . PHP_EOL, date('Y-m-d H:i:s'), $msg)); 
   fclose($handle); 
  } catch (Exception $e) { 
   // null; 
  } 
 } 
}