Modified Wordpress datalayer variables for pulling: author names, post types, number of comments, categories, tags and dates into custom variables for the classic version of Google Analytics. Original script provided by Julien Coquet at: http://goo.gl/t3bz0M

Wordpress Data Layer Variables

<script type="text/javascript">
// URL toolbox - helps grabbing elements in the URL
var _d = document;
var _dl = _d.location;
var _dlp = _dl.pathname;
var _dls = _dl.search;
var _dr = _d.referrer;

// Initialize your data layer and start pushing variables from custom WordPress PHP data layer
dataLayer.push({
<?php if (is_404()){
// 404 pages, handled with a /404/ prefix as well as the referrer ?>
"GTM_WP_404": "<?php print is_404(); ?>",
"GTM_WP_404_URL": "/404" + _dlp + "/"+ _dr,
<?php } ?>
<?php if(is_home()){
// Home page is tagged manually here but can be done directly in GTM
?>
"GTM_WP_post_type": "Home",
"GTM_WP_Category": "Home",
<?php } ?>

<?php if (is_single()||is_page()){
/* Content pages: either a post or a page
*  Query the WP API to retrieve post/page type, author, number of comments, tag, or even custom variables
*/
$gtm_cat = get_the_category();

//Get author ID

// post/page tags being passed as one big string separated by spaces
$posttags = get_the_tags();
if ($posttags) {
foreach($posttags as $tag) {
$gtm_tags .= $tag->name . ' , ';
}
}

// Now we populate the Javascript data layer with our PHP variables
?>
"GTM_WP_authorname": "<?php the_author(); ?>",
"GTM_WP_post_type": "<?php print get_post_type(); ?>",
"GTM_WP_Number_Comments": "<?php print get_comments_number(); ?>",
"GTM_WP_Category": "<?php print $gtm_cat[0]->cat_name; ?>",
"GTM_WP_Tags": "<?php print trim($gtm_tags); ?>",
<?php }
// Done with WordPress page type/conditions, you can add more default dataLayer variables below ?>
"GTM_WP_date": "<?php print the_date( $format, $before, $after, $echo ); ?>"
});
// Don't forget to terminate your data layer correctly!
</script>

Thought I would share a more up to date snippet here for other users.

https://gist.github.com/BryanBarrera/124c934fd375c7509e74