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