！ ReadFile download local server Test no problem, but upload to the space server is not recognized file size

Help! ReadFile download local server Test no problem, but upload to the space server is not recognized file size
Help! ReadFile download local server Test no problem, but upload to the space server is unable to identify the size of the file, I novice, but also look master pointing twos!

 
  

 
  $sql = "SELECT * from Lxy_download";
$result =mysql_query ($sql);
while ($row =mysql_fetch_assoc ($result)) {
{
?>

 
  
$file _dir = "system32/upload/download/";
$filesize =filesize ("$file _dir/$file _name");  
    Header (' Content-type:application/octet-stream ');  
    Header (' content-ranges:bytes ');  
    Header (' content-length: '. $filesize);  
    Header (' content-disposition:attachment; filename= '. $file _name);  

Flush ();  
    ReadFile ("$file _dir/$file _name");
Exit (0);
}
?>

 
  }
?>

------to solve the idea----------------------
$FileFile? This $filefile is a get or post.
Most servers do not turn on automatic conversion of request parameters into variables.
Just try it with $_get[' filefile ' or $_post[' filefile ')

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