Create a thumbnail file when uploading?

I have been trying to find a way to create a thumbnail file upon uploading an image. So basically, after the image has been uploaded, I will need to call a function to copy the image, resize it, and rename it to, for example, imagename_thumb.gif

I've got a working script to resize and rename a file in the directory. However, I am a PHP beginner and really struggles in finding out how to do this over the MCPUK mode.

All I can think of is this:
On the filemanager/browser/mcpuk/frmupload.html, on this line:
<form id="frmUpload" action="" target="frmUploadWorker" method="post" enctype="multipart/form-data" onSubmit="return OnSubmit();">

.. I put another onSubmit method, eg CreateThumbnail(), so it would be like this:

<form id="frmUpload" action="" target="frmUploadWorker" method="post" enctype="multipart/form-data" onSubmit="return OnSubmit(); CreateThumbnail()">

The problem is, I need to know which folder the file currently resides, and the name of the file I have just uploaded. Furthermore, I need to be able to automatically rewrite the old thumbnail, if exists.

Can someone help me on how to put this together?

Anyways, here's the script that I have tried (separately from fckeditor) to resize an image:

<?php

// find out the current size info 
$photo_filename = "big.jpg";
$new_photo_filename = "big_thumb.jpg";
$path = "/var/www/vhosts/theurl.com/images/";

$image_stats = GetImageSize($path.$photo_filename); 
$imagewidth = $image_stats[0]; 
$imageheight = $image_stats[1]; 
$img_type = $image_stats[2]; 
$new_w = 100; $ratio = ($imagewidth / $new_w); 
$new_h = round($imageheight / $ratio);

// Find out if we need to resize it by checking to 
// see if the file needs resizing and making sure the 
// resized version does not exist yet 
 
if (($imagewidth > $new_w)&& (!file_exists($path.$new_photo_filename))) {
 
// if this is a jpeg, resize as a jpeg 
if ($img_type==2) { 
$src_img = imagecreatefromjpeg($path.$photo_filename); 
$dst_img = imagecreate($new_w,$new_h);
imagecopyresized($dst_img,$src_img,0,0,0,0,$new_w,$new_h,imagesx($src_img),imagesy($src_img));

$imageresize = imagejpeg($dst_img, $path.$new_photo_filename);
 
if (!$imageresize) {
    echo ('Failed');
} else {
    echo ('Succeed');
}
 
} elseif ($img_type==3) {
// if image is a png, copy it 
 
$dst_img=ImageCreate($new_w,$new_h); 
$src_img=ImageCreateFrompng($path.$photo_filename);
ImageCopyResized($dst_img,$src_img,0,0,0,0,$new_w,$new_h,ImageSX($src_img),ImageSY($src_img)); 
Imagepng($dst_img, $path.$new_photo_filename);
 
 
// Normally if image is neither png nor jpeg (ie, invalid image or a gif file), I use 
// the fullsize as the thumbnail and just resize it through the html size tags. For this 
 // example tho, we’ll pretend we have a hacked version of Gdlib
 
 } elseif ($img_type==1) { 
$dst_img=ImageCreate($new_w,$new_h); 
$src_img=ImageCreateFromGif($path.$photo_filename);
ImageCopyResized($dst_img,$src_img,0,0,0,0,$new_w,$new_h,ImageSX($src_img),ImageSY($src_img)); 
ImageGif($dst_img, $path.$new_photo_filename);
 
 } else { 
// if it doesn’t show up as any of the valid formats, give an error 
 
 
} // endif img_type sequence
 
 
} 

?>

Thanks in advance for your help. I really need this. Thanks!