Can't display image field type with php

I created an image field type and it displays the link to the image while using the shortcode, but when i try displaying it with php it outputs “Array”.

This is the code i use to display the value:
<?php $cover = get_post_meta( get_the_ID(), 'cover', true ); echo $cover; ?>
I use the same code to display other fields and it works fine.
Field Label: Cover
Field name: cover

https://wordpress.org/plugins/pods/