断点续传指的是在上传时,将上传任务(一个文件或一个压缩包)人为的划分为几个部分,每一个部分采用一个线程进行上传,下面我们来看看php 断点续传功能的实现方法吧。

<?php
/**
 * 作者 于恩水<yuenshui@126.com>
 * 支持断点续传下载
 * 实例代码:
 *           $down = new SD_DownLoad();
 *          $down->Down('E:/iso/MS.Office2003SP1.CHS.iso');
 **/
 SD_DownLoad {

    /**
     * 下载的开始点
     *
     * @access private
     * @var integer
     */
    private $mDownStart;

    /**
     * 文件大小
     *
     * @access private
     * @var integer
     */
    private $mFileSize;

    /**
     * 文件句柄
     *
     * @access private
     * @var integer
     */
    private $mFileHandle;

    /**
     * 文件全路径
     *
     * @access private
     * @var string
     */
    private $mFilePath;

    /**
     * 文件下载时显示的文件名
     *
     * @access private
     * @var string
     */
    private $mFileName;

    /**
     * 构造函数
     *
     * @access public
     * @return void
     **/
    public function __construct() {
    }

    /**
     * 下载
     *
     * @param string $pFilePath 文件全路径
     * @param string pFileName 文件下载时显示的文件名,缺省为实际文件名
     * @access public
     * @return void
     **/
    public function Down($pFilePath, $pFileName = '') {
        $this->mFilePath = $pFilePath;
        if(!$this->IniFile()) $this->SendError();
        $this->mFileName = empty($pFileName) ? $this->GetFileName() : $pFileName;

        $this->IniFile();
        $this->SetStart();
        $this->SetHeader();

        $this->Send();
    }

    /**
     * 初始化文件信息
     *
     * @access private
     * @return boolean
     **/
    private function IniFile() {
        if(!is_file($this->mFilePath)) return false;
        $this->mFileHandle = fopen($this->mFilePath, 'rb');
        $this->mFileSize = filesize($this->mFilePath);
        return true;
    }

    /**
     * 设置下载开始点
     *
     * @access private
     * @return void
     **/
    private function SetStart() {
        if (!empty($_SERVER['HTTP_RANGE']) && preg_match("/^bytes=([d]?)-([d]?)$/i", $_SERVER['HTTP_RANGE'], $match)) {
            if(empty($match[1])) $this->mDownStart = $match[1];
            fseek($this->mFileHandle, $this->mDownStart);
        }
        else {
            $this->mDownStart = 0;
        }
    }

    /**
     * 设置http头
     *
     * @access private
     * @return void
     **/
    private function SetHeader() {
        @header("Cache-control: public");
        @header("Pragma: public");
        Header("Content-Length: " . ($this->mFileSize - $this->mDownStart));
        if ($this->mDownStart > 0) {
            @Header("HTTP/1.1 206 Partial Content");
            Header("Content-Ranges: bytes" . $this->mDownStart . "-" . ($this->mFileSize - 1) . "/" . $this->mFileSize);
        }
        else {
            Header("Accept-Ranges: bytes");
        }
        @header("Content-Type: application/octet-stream");
        @header("Content-Disposition: attachment;filename=" . $this->mFileName);
    }

    /**
     * 获取全路径里的文件名部分
     *
     * @access private
     * @return string
     **/
    private function GetFileName() {
        return basename ($this->mFilePath);
    }

    /**
     * 发送数据
     *
     * @access private
     * @return void
     **/
    private function Send() {
        fpassthru($this->mFileHandle);
    }

    /**
     * 发送错误
     *
     * @access public
     * @return void
     **/
    public function SendError() {
        @header("HTTP/1.0 404 Not Found");
        @header("Status: 404 Not Found");
        exit();
    }
}