class.upload.php is a powerful and mature PHP class to manage uploaded files, and manipulate images in many ways. The script is available under a GPL license.
Check the log produced by the class. The txt extension is added if the file is thought to be dangerous. Check the MIME types detection on your server, and see in the logs why you get the txt extension added.
You can also use file_is_image to process your file differently if it is not an image.Reply
You can also use file_is_image to process your file differently if it is not an image.