文件下载问题

Question

<?
$filename; //要保存的文件名 
$$content; //文件内容,从数据库中读出来$mime_type=(USR_BROWSER_AGENT=='IE'||USR_BROWSER_AGENT=='OPERA')?'application/octetstream':'application/octet-stream';header ('Content-Type:'.$mime_type);
$content_disp =(USR_BROWSER_AGENT =='IE')?'inline':'attachment';
header ('Content-Disposition:'.$content_disp.';filename="'.$filename.'"');
header ('Pragma: no-cache');
header ('Expires: 0');
echo $content;
?>