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.
more info about the class
if($handle->image_src_x > $handle->image_src_y) {.... } //this means landscape if($handle->image_src_x < $handle->image_src_y) {..... } //this means portrait
for whoever else is wondering.