Description:
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I use readfile() function to force download ftp file.In PHP4.3.4 version,the file size display unknow.But in PHP 5.0 the it works correctly.But they are also occur error when the FTP file size is large to 40M~50M.

Reproduce code:
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<?php 
$filename = $_COOKIE["url"];//ftp request
header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0"); 
header("Content-Type: application/force-download");
header("Content-Type: application/octet-stream");
header("Content-Type: application/download");
header("Content-Disposition: attachment; filename=".basename($filename).";");
header("Content-Transfer-Encoding: binary");
header("Content-Length: ".filesize($filename));
@readfile("$filename"); 
exit();
?> 

Expected result:
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      USE IN FORCE DOWNLOAD FTP FILE

 PHP 4.0 :If file size > 40M~50M,connection auto reset and download dialog closed.

 PHP 5.0 :If file size > 40M~50M,server cant response the request,download stoped,but download dialog still open,only not any response.

 But if file size <40M~50M,they are works fine.