Add star ratings to the Product category page and by the product name on the single product page

functions.php

<?php

add_action( 'woocommerce_after_shop_loop_item','show_rating_stars' );
add_action( 'woocommerce_single_product_summary','show_rating_stars',15 );
function show_rating_stars() {

	global $woocommerce,$post, $wpdb;
	if ( comments_open() ) :

		$count = $wpdb->get_var("
							SELECT COUNT(meta_value) FROM $wpdb->commentmeta
							LEFT JOIN $wpdb->comments ON $wpdb->commentmeta.comment_id = $wpdb->comments.comment_ID
							WHERE meta_key = 'rating'
							AND comment_post_ID = $post->ID
							AND comment_approved = '1'
							AND meta_value > 0
							");

		$rating = $wpdb->get_var("
							SELECT SUM(meta_value) FROM $wpdb->commentmeta
							LEFT JOIN $wpdb->comments ON $wpdb->commentmeta.comment_id = $wpdb->comments.comment_ID
							WHERE meta_key = 'rating'
							AND comment_post_ID = $post->ID
							AND comment_approved = '1'
							");

		if ( $count > 0 ) :

			$average = number_format($rating / $count, 2);

			echo '<div itemprop="aggregateRating" itemscope itemtype="http://schema.org/AggregateRating"';
			if ( is_product() ) : 
				echo ' class="single_product_rating"';
			else :
				echo ' class="loop_rating"';
			endif;
			echo '>';

			echo '<div class="star-rating" title="'.sprintf(__('Rated %s out of 5', 'woocommerce'), $average).'"><span style="width:'.($average*16).'px"><span itemprop="ratingValue" class="rating">'.$average.'</span> '.__('out of 5', 'woocommerce').'</span></div>';

			echo '</div>';

			if ( is_product() ) : 
				echo '<div class="clear"></div>';
			else :
				echo '';
			endif;

		endif;

	endif;

}

?>

Hello,
I tried this in my functions.php but it is not working.