分享一个超好用的php header下载函数

复制代码 代码如下:
<?php
/**
 * 发送文件
 *
 * @author: legend(legendsky@hotmail.com)
 * @link: http://www.ugia.cn/?p=109
 * @description: send file to client
 * @version: 1.0
 *
 * @param string   $fileName      文件名称或路径
 * @param string   $fancyName     自定义的文件名,为空则使用filename
 * @param boolean  $forceDownload 是否强制下载
 * @param integer  $speedLimit    速度限制,单位为字节,0为不限制,不支持windows服务器
 * @param string   $$contentType  文件类型,默认为application/octet-stream
 *
 * @return boolean
 */
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 == "")
            {
                $endPos = $fileSize - 1;
            }

            $startPos = $startPos < 0 ? 0 : $startPos;
            $endPos = $endPos > $fileSize - 1 ? $fileSize - 1 : $endPos;

            $length = $endPos - $startPos + 1;

            if ($length < 0)
            {
                return false;
            }

            $contentLength = $length;
            $isPartial = true;
        }
    }    // send headers
    if ($isPartial)
    {
        header("HTTP/1.1 206 Partial Content");
        header("Content-Range: bytes $startPos-$endPos/$fileSize");    }
    else
    {
        header("HTTP/1.1 200 OK");
        $startPos = 0;
        $endPos = $contentLength - 1;
    }

    header("Pragma: cache");
    header("Cache-Control: public, must-revalidate, max-age=0");
    header("Accept-Ranges: bytes");
    header("Content-type: " . $contentType);
    header("Content-Length: " . $contentLength);    if ($forceDownload)
    {
        header("Content-Disposition: attachment; filename="" . rawurlencode($fancyName). """);//汉字自动转为URL编码
  header("Content-Disposition: attachment; filename="" . $fancyName. """);
    }

    header("Content-Transfer-Encoding: binary");    $bufferSize = 2048;

    if ($speedLimit != 0)
    {
        $packetTime = floor($bufferSize * 1000000 / $speedLimit);
    }

    $bytesSent = 0;
    $fp = fopen($fileName, "rb");
    fseek($fp, $startPos);

    //fpassthru($fp);    while ($bytesSent < $contentLength && !feof($fp) && connection_status() == 0 )
    {
        if ($speedLimit != 0)
        {
            list($usec, $sec) = explode(" ", microtime());
            $outputTimeStart = ((float)$usec + (float)$sec);
        }

        $readBufferSize = $contentLength - $bytesSent < $bufferSize ? $contentLength - $bytesSent : $bufferSize;
        $buffer = fread($fp, $readBufferSize);       

        echo $buffer;

        ob_flush();
        flush();

        $bytesSent += $readBufferSize;        if ($speedLimit != 0)
        {
            list($usec, $sec) = explode(" ", microtime());
            $outputTimeEnd = ((float)$usec + (float)$sec);            $useTime = ((float) $outputTimeEnd - (float) $outputTimeStart) * 1000000;
            $sleepTime = round($packetTime - $useTime);
            if ($sleepTime > 0)
            {
                usleep($sleepTime);
            }
        }
    }
   

    return true;
}
 ?>