PHP使用range协议实现输出文件断点续传代码实例

range协议用途：一般是用在断点续传的时候，但是实际的用户很大，例如你的web server需要输出一个大文件，那么用range可以分段输出，缓解压力。同时在提供音乐视频等服务时可以缓冲下载，如果用户中途关闭，可以节约网络带宽。

    <?php

    // 文件名
    $filename = $_GET ['filename'];

    // 文件路径
    $location = 'media/' . $filename;

    // 后缀
    $extension = substr ( strrchr ( $filename, '.' ), 1 );

    if ($extension == "mp3") {
        $mimeType = "audio/mpeg";
    } else if ($extension == "ogg") {
        $mimeType = "audio/ogg";
    }

    if (! file_exists ( $location )) {
        header ( "HTTP/1.1 404 Not Found" );
        return;
    }

    $size = filesize ( $location );
    $time = date ( 'r', filemtime ( $location ) );

    $fm = @fopen ( $location, 'rb' );
    if (! $fm) {
        header ( "HTTP/1.1 505 Internal server error" );
        return;
    }

    $begin = 0;
    $end = $size - 1;

    if (isset ( $_SERVER ['HTTP_RANGE'] )) {
        if (preg_match ( '/bytes=\h*(\d+)-(\d*)[\D.*]?/i', $_SERVER ['HTTP_RANGE'], $matches )) {
            // 读取文件，起始节点
            $begin = intval ( $matches [1] );

            // 读取文件，结束节点
            if (! empty ( $matches [2] )) {
                $end = intval ( $matches [2] );
            }
        }
    }

    if (isset ( $_SERVER ['HTTP_RANGE'] )) {
        header ( 'HTTP/1.1 206 Partial Content' );
    } else {
        header ( 'HTTP/1.1 200 OK' );
    }

    header ( "Content-Type: $mimeType" );
    header ( 'Cache-Control: public, must-revalidate, max-age=0' );
    header ( 'Pragma: no-cache' );
    header ( 'Accept-Ranges: bytes' );
    header ( 'Content-Length:' . (($end - $begin) + 1) );

    if (isset ( $_SERVER ['HTTP_RANGE'] )) {
        header ( "Content-Range: bytes $begin-$end/$size" );
    }

    header ( "Content-Disposition: inline; filename=$filename" );
    header ( "Content-Transfer-Encoding: binary" );
    header ( "Last-Modified: $time" );

    $cur = $begin;

    // 定位指针
    fseek ( $fm, $begin, 0 );

    while ( ! feof ( $fm ) && $cur <= $end && (connection_status () == 0) ) {
        print fread ( $fm, min ( 1024 * 16, ($end - $cur) + 1 ) );
        $cur += 1024 * 16;
    }

range协议官方文档：http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html