Better way to get Wordpress post featured image

functions.php

<?php
/**
 * Get everything you could ever want about a featured image
 *
 * Usage: 
 * <?php $image = get_featured_image(); ?>
 * <img class="thumbnail" src="<?php echo $image['url']; ?>" alt="<?php echo $image['title']; ?>">
 * 
 * @param integer|object $post_id The ID/Object of the post that has the desired post thumbnail image
 * @return false|array Null on failure to find the image, wp_prepare_attachment_for_js array on success
 * 
 */
if (!function_exists('get_featured_image')) {
	function get_featured_image($post_id = null) {
		if (!$post_id) {
			global $post;
			$post_id = $post->ID;

			if (!$post_id) return false;
		}
		return wp_prepare_attachment_for_js( get_post_thumbnail_id( $post_id ) );
	}
}
?>