Output image thumbnail with link to full size image

gistfile1.phtml

<?php

	$sample_gallery_images = get_custom_field( 'sample_gallery_images' );

	// If field value is empty don't output anything
	if( ! empty( $sample_gallery_images ) && function_exists( 'job_manager_get_resized_image' ) ){

		// If it's an array that means there are multiple images
		if( is_array( $sample_gallery_images ) ){
			foreach( $sample_gallery_images as $gallery_image ){

				$thumbnail_image = job_manager_get_resized_image( $gallery_image, 'thumbnail' );
				// This outputs an image with a link to the image itself with a line break after each image
				echo '<a href="' . $gallery_image '" target="_blank"><img src="' . $thumbnail_image . '" class="some_custom_class" /></a><br />';

			}
		// Otherwise it's a single image URL
		} else {
			$thumbnail_image = job_manager_get_resized_image( $sample_gallery_images, 'thumbnail' );
			// This outputs an image with a link to the image itself
			echo '<a href="' . $sample_gallery_images '" target="_blank"><img src="' . $thumbnail_image . '" class="some_custom_class" /></a>';
		}

	}
?>