HTTP Header Range用途:一般是用在断点续传的时候。但是实际的用途很广,例如你的服务器需要输出一个大文件,那么可以用range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
$filename=$_GET['filename'];
$location='media/'.$filename;

$extension = substr(strrchr($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))
    {
        $begin  = intval($matches[1]);
        if (!emptyempty($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  = $begin;
fseek($fm, $begin, 0);

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

?>

参考:

HTTP Header详解

HTTP/1.1: Header Field Definitions