word document is not correct after downloaded

hello everyone.. can anybody help me?
i made an application to upload files to the server..
and after that use ris able to download that file again..
but after downloading the file (specifically word document), i found that the content is not correct..

lets say the original content is "This is a word document"..after downloading the file..the content becomes "&@%&*@**)@!)(!@)((___@!#" (some invalid unreadable characters)..
what cause this error? i also cannot view a jpeg document after downloading it..

here's the script for my download.php :

<?
ob_start();
session_start();

include 'config.php';
include 'opendb.php';

$query = "SELECT * FROM phpgw_dts_attachment WHERE att_id = ".$_REQUEST['att_id'];
$result = mysql_query($query, $db);

if ($result){
while($row = mysql_fetch_array($result))
{
$att_name = $row['att_name'];
$att_path = $row['att_path'];
$location = $att_path.$row['att_tempname'];
$att_type = $row['att_type'];
}
}
header('Content-Disposition: attachment; filename="'.$att_name.'"');
header("Cache-Control: must-revalidate");
header("Content-Type: ".$att_type);
readfile($location);

//ini_set('zlib.output_compression','Off');

exit();
?>

can anyone help me with this?

re: word document is not correct after downloaded

hmmm

if you try to view in browser the word it's normal to see that caracter
download the file and open it with microsoft word.
header("Content-Type: application/octet-stream");

Note: i see that you user a blob to store the file. Maybe the blob it's to small i notice from my experience that a program manager for database can create only blob with small storage capability. It's useful to manually create the blob colum by using a php script.