php发送文件
<?php
function sendFile($fileName, $fancyName = '', $forceDownload = true, $speedLimit = 0, $contentType = '')
{
    if (!is_readable($fileName))
    {
        header("HTTP/1.1 404 Not Found");
        return false;
    }


    $fileStat = stat($fileName);
    $lastModified = $fileStat['mtime'];


    $md5 = md5($fileStat['mtime'] .'='. $fileStat['ino'] .'='. $fileStat['size']);
    $etag = '"' . $md5 . '-' . crc32($md5) . '"';


    header('Last-Modified: ' . gmdate("D, d M Y H:i:s", $lastModified) . ' GMT');
    header("ETag: $etag");


    if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) && strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) >= $lastModified)
    {
        header("HTTP/1.1 304 Not Modified");
        return true;
    }


    if (isset($_SERVER['HTTP_IF_UNMODIFIED_SINCE']) && strtotime($_SERVER['HTTP_IF_UNMODIFIED_SINCE']) < $lastModified)
    {
        header("HTTP/1.1 304 Not Modified");
        return true;
    }


    if (isset($_SERVER['HTTP_IF_NONE_MATCH']) &&  $_SERVER['HTTP_IF_NONE_MATCH'] == $etag)
    {
        header("HTTP/1.1 304 Not Modified");
        return true;
    }


    if ($fancyName == '')
    {
        $fancyName = basename($fileName);
    }


    if ($contentType == '')
    {
        $contentType = 'application/octet-stream';
    }


    $fileSize = $fileStat['size'];


    $contentLength = $fileSize;
    $isPartial = false;


    if (isset($_SERVER['HTTP_RANGE']))
    {
        if (preg_match('/^bytes=(\d*)-(\d*)$/', $_SERVER['HTTP_RANGE'], $matches))
        {
            $startPos = $matches[1];
            $endPos = $matches[2];


            if ($startPos == '' && $endPos == '')
            {
                return false;
            }


            if ($startPos == '')
            {
                $startPos = $fileSize - $endPos;
                $endPos = $fileSize - 1;
            }
            else if ($endPos == '')