Caching images using PHP Image Cache - php

Question

I am using this image caching library (http://nielse63.github.io/php-image-cache/) to cache images I am getting using the OMBD API (http://omdbapi.com/).
This is my setup:
$imagecache = new ImageCache();
$imagecache->cached_image_directory = '/img/cache/';
$imagecache->cached_image_url = '/img/cache';
$cached_src_two = $imagecache->cache( 'http://image.tmdb.org/t/p/original/eYVZP9CibJg1fyZnZahfFIYqfPr.jpg' );
echo 'Original file size: ' . filesize($imagecache->image_src) . ' bytes<br>';
echo 'PHPImageCach-ified file size: ' . filesize($imagecache->cached_filename) . ' bytes<br>';
echo 'Total image size reduction: ' . (((filesize($imagecache->image_src) - filesize($imagecache->cached_filename)) / filesize($imagecache->image_src))*100) . '%';
echo '<img src="'.$cached_src_two.'" alt="">';
I am not getting any errors. But something weird is going on I can't understand. It is saving a local copy of the image in $imagecache->cached_image_directory - this is not compressed or cached. Then it is creating another file in the img directory.
I assume this is the cached file, but I am unable to open it to check. The cached filename looks like: eYVZP9CibJg1fyZnZahfFIYqfPr.jpg.jpeg
Note the jpg.jpeg. Even fixing the file extension does not work. I can't find anything useful in the documentation. What is going wrong here?