exif_thumbnail() reads the embedded thumbnail of a TIFF or JPEG image.
If you want to deliver thumbnails through this function, you should send the mimetype information using the header() function.
The parameters width, height and imagetype are available since PHP 4.3.0 and return the size of the thumbnail as well as its type. It is possible that exif_thumbnail() cannot create an image but can determine its size. In this case, the return value is FALSE but width and height are set.
Starting from version PHP 4.3.0, the function exif_thumbnail() can return thumbnails in TIFF format.
If the image contains no thumbnail, FALSE will be returned. Otherwise the embedded thumbnail is returned.