How to preserve the file name when downloading pic & midi

Hi everybody,

Below is a code that delivers (in this case) a picture to user. Let's name it download.php. When I run this program in IE, the file is named as it should be (somepicture.gif) and saves to a disk. But the problem is when I try to save it to my mobile phone via WAP site.
An image (or midi) is successfuly received and viewed on my phone screen, but I cannot save it under its original name. It's saved as download.php and afterwards, when I disconnect, my phone does not recognize it as an image.
I know that this also depends of the type of mobile phone. Some phones manage to save the image, but looses the file name also.

So, the question is: How can I preserve file name when downloading picture to my phone? Is it possible?


THE CODE:

<?php
$filename='somepicture.gif';
$size=5478;
$requested_file = '/app/wap/download/'.$filename;
if (file_exists($requested_file)) {
header('Content-Type: image/gif');
header('Expires: ' . gmdate('D, d M Y H:i:s') . ' GMT');
header('Content-Disposition: attachment; filename="'.$filename.'"');
header('Content-Length: '.$size);
readfile($requested_file);
}
exit();
?>


THANX!