求帮看下这段PHP下载MP4文件的有关问题，文件下载不完整-PHP Tutorial-php.cn

求帮看下这段PHP下载MP4文件的问题，文件下载不完整

function dl_file($file){
 $len = filesize($file);
 $filename = basename($file);
 $file_extension = strtolower(substr(strrchr($filename,"."),1));
 switch( $file_extension ) {
 case "mp4": $ctype="video/mp4"; break;
 default: $ctype="application/force-download";
 }
 header("Pragma: public");
 header("Expires: 0");
 header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
 header("Cache-Control: public"); 
 header("Content-Description: File Transfer");
 header("Content-Type: $ctype");
 $header="Content-Disposition: attachment; filename=".$filename."";
 header($header );
 header("Content-Transfer-Encoding: binary");
 header("Content-Length: ".$len);
 ob_clean();
 flush();
 readfile($file);
 exit;
}
dl_file('test.mp4');

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在火狐，谷歌浏览器下载正常，IE和迅雷下载文件不完整
------解决方案--------------------
ob_clean();
flush();
readfile($file);
------解决方案--------------------
没加mime头
------解决方案--------------------
header("Content-Transfer-Encoding: binary");
header("Content-Length: ".$len);
这俩删掉试试
------解决方案--------------------
nginx + php 环境下没有你说的那个问题，ie和迅雷都可以正常下载不过我的文件是flv，这样的话也只能说明是mime头出错了
我的代码如下：

function dl_file($file){
$len = filesize($file);
$filename = basename($file);
$file_extension = strtolower(substr(strrchr($filename,"."),1));
switch( $file_extension ) {
case "mp4": $ctype="video/mp4"; break;
default: $ctype="application/force-download";
}
header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Cache-Control: public");
header("Content-Description: File Transfer");
header("Content-Type: $ctype");
$header="Content-Disposition: attachment; filename=".$filename."";
header($header );
header("Content-Transfer-Encoding: binary");
header("Content-Length: ".$len);
ob_clean();
flush();
readfile($file);
exit;
}
dl_file('http://res.805.com/videos/霍山·上林后苑(易仟亿集团) [640x480].flv'); 只改了一个文件名而已其他的都没变