PHP实现 断点续传

所谓断点续传，也就是要从文件已经下载的地方开始继续下载。在以前版本的 HTTP 协议是不支持断点的，HTTP/1.1 开始就支持了。

新建一个类：FileDownload.class.php

<?php  /**  * Created by PhpStorm.  * User: 63448  * Date: 2018/7/4  * Time: 19:46  */  /** php下载类,支持断点续传  * download: 下载文件  * setSpeed: 设置下载速度  * getRange: 获取header中Range  */ class FileDownload
{

    /** 下载  * @param String $file 要下载的文件路径  * @param String $name 文件名称,为空则与下载的文件名称一样  * @param boolean $reload 是否开启断点续传  */  public function download($file, $name = '', $reload = false)
    {
        $fp = @fopen($file, 'rb');
        if ($fp) {
            if ($name == '') {
                $name = basename($file);
            }
            $header_array = get_headers($file, true);
            //var_dump($header_array);die;
            // 下载本地文件，获取文件大小
            if (!$header_array) {
                $file_size = filesize($file);
            } else {
                $file_size = $header_array['Content-Length'];
            }
            $ranges = $this->getRange($file_size);
            $ua = $_SERVER["HTTP_USER_AGENT"];//判断是什么类型浏览器
            header('cache-control:public');
            header('content-type:application/octet-stream');

            $encoded_filename = urlencode($name);
            $encoded_filename = str_replace("+", "%20", $encoded_filename);

            //解决下载文件名乱码
            if (preg_match("/MSIE/", $ua) || preg_match("/Trident/", $ua)) {
                header('Content-Disposition: attachment; filename="' . $encoded_filename . '"');
            } else if (preg_match("/Firefox/", $ua)) {
                header('Content-Disposition: attachment; filename*="utf8\'\'' . $name . '"');
            } else if (preg_match("/Chrome/", $ua)) {
                header('Content-Disposition: attachment; filename="' . $encoded_filename . '"');
            } else {
                header('Content-Disposition: attachment; filename="' . $name . '"');
            }
            //header('Content-Disposition: attachment; filename="' . $name . '"');

            if ($reload && $ranges != null) { // 使用续传
                header('HTTP/1.1 206 Partial Content');
                header('Accept-Ranges:bytes');

                // 剩余长度
                header(sprintf('content-length:%u', $ranges['end'] - $ranges['start']));

                // range信息
                header(sprintf('content-range:bytes %s-%s/%s', $ranges['start'], $ranges['end'], $file_size));
                //file_put_contents('test.log',sprintf('content-length:%u',$ranges['end']-$ranges['start']),FILE_APPEND);
                // fp指针跳到断点位置
                fseek($fp, sprintf('%u', $ranges['start']));
            } else {
                file_put_contents('test.log', '2222', FILE_APPEND);
                header('HTTP/1.1 200 OK');
                header('content-length:' . $file_size);
            }

            while (!feof($fp)) {
                //echo fread($fp, round($this->_speed*1024,0));
                //echo fread($fp, $file_size);
                echo fread($fp, 4096);
                ob_flush();
            }

            ($fp != null) && fclose($fp);
        } else {
            return '';
        }
    }

    /** 设置下载速度  * @param int $speed  */  public function setSpeed($speed)
    {
        if (is_numeric($speed) && $speed > 16 && $speed < 4096) {
            $this->_speed = $speed;
        }
    }

    /** 获取header range信息  * @param int $file_size 文件大小  * @return Array  */  private function getRange($file_size)
    {
        //file_put_contents('range.log', json_encode($_SERVER), FILE_APPEND);
        if (isset($_SERVER['HTTP_RANGE']) && !empty($_SERVER['HTTP_RANGE'])) {
            $range = $_SERVER['HTTP_RANGE'];
            $range = preg_replace('/[\s|,].*/', '', $range);
            $range = explode('-', substr($range, 6));
            if (count($range) < 2) {
                $range[1] = $file_size;
            }
            $range = array_combine(array('start', 'end'), $range);
            if (empty($range['start'])) {
                $range['start'] = 0;
            }
            if (empty($range['end'])) {
                $range['end'] = $file_size;
            }
            return $range;
        }
        return null;
    }
}

新建一个PHP文件：FileDownload.php

<?php /**  * Created by PhpStorm.  * User: 63448  * Date: 2018/7/4  * Time: 19:47  */ require_once 'FileDownload.class.php';//引用类
$obj = new FileDownload();//实例化FileDownload
$obj->download('文件路径', '文件夹名', true);//调用方法（true是开启续传）