print_blog_thumbnail.php

<?php
// print the blog thumbnail
function print_blog_thumbnail( $post_id, $item_size ) {
  if( empty($item_size) ){ return ''; }

	$thumbnail_types = get_post_meta( $post_id, 'post-option-thumbnail-types', true);
	if( $thumbnail_types == "Image" || empty($thumbnail_types) ){
		$thumbnail_id = get_post_thumbnail_id( $post_id );
		$thumbnail = wp_get_attachment_image_src( $thumbnail_id , $item_size );
		$alt_text = get_post_meta($thumbnail_id , '_wp_attachment_image_alt', true);
		if( !empty($thumbnail) ){
			echo '<div class="blog-media-wrapper gdl-image">';
			echo '<a href="' . get_permalink() . '"><img src="' . $thumbnail[0] .'" alt="'. $alt_text .'"/></a>';
			echo '</div>';	// blog-media-wrapper
		}
	}
	else if( $thumbnail_types == "Video" ){
		$video_link = get_post_meta( $post_id, 'post-option-thumbnail-video', true); 
		echo '<div class="blog-media-wrapper gdl-video">';
		echo get_video($video_link, gdl_get_width($item_size), gdl_get_height($item_size));
		echo '</div>';	// blog-media-wrapper
	}
	else if ( $thumbnail_types == "Slider" ){
		$slider_xml = get_post_meta( $post_id, 'post-option-thumbnail-xml', true); 
		$slider_xml_dom = new DOMDocument();
		$slider_xml_dom->loadXML($slider_xml);
		echo '<div class="blog-media-wrapper gdl-slider">';
		echo print_flex_slider($slider_xml_dom->documentElement, $item_size);
		echo '</div>';	// blog-media-wrapper
	}
	else if ( $thumbnail_types == "HTML5 Video" ){
		$video = get_post_meta( $post_id, 'post-option-thumbnail-html5-video', true); 
		echo '<div class="blog-media-wrapper gdl-html5-video">';
		get_html5_video($video);
		echo '</div>';	// blog-media-wrapper		
	}	
}