Looks like you are not passing image file name to the script. Script needs to know which image needs thumbnail. It cannot convert all images in the folder (yet, i think i'll add this feature). Note: i just uploaded updated
thumbnail generator.
It depends on how you want to generate thumbnail. Thumbnail can be generated from browser (passing all parameters via url) or from your existing php script (setting parameters in the script).
Note: description says for images and thumbs folders - "MUST end with slash". You did not put slash at the end. Also you put space at the end, which will cause problems.
Via URL:
http://example.com/path/to/thumb.php?src=image.jpg&dest=thumbname.jpg
It will search for image.jpg in the $images_filder (you set it in the thumb.php) and will create thumbnail thumbname.jpg in the $thumbs_folder (you set it in the thumb.php)
If you want to create thumbs from your program then add following code to your program
// include image processing code
include('image.class.php');
$img = new Zubrag_image;
// initialize
$img->max_x = max_thumb_width; // ex 100
$img->max_y = max_thumb_height; // ex 100
$img->cut_x = cut_width_before_creating_thumb; // ex 800, set to 0 to skip
$img->cut_y = cut_height_before_creating_thumb; // ex 600, set to 0 to skip
$img->quality = image_quality; // 0 to 100, 0 - bad, 100 best
$img->save_to_file = $save_to_file; // 1 - save to file, 0 - output in browser
$img->image_type = $image_type; // -1 - use default, 1 = save as GIF, 2 = JPG, 3 = PNG
// generate thumbnail
$img->GenerateThumbFile(path_to_source_image, thumbnail_path);