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。
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<?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;
}
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range协议官方文档：http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html