WordPress Google Tag Manager Data Layer

datalayer.php

<!-- K Google Tag Manager Data Layer -->
<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(); // post/page tags being passed as one big string separated by spaces 
	$posttags = get_the_tags(); 
	if ($posttags) { 
        $gtm_tags = '';
		foreach($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_Category': '<?php if ( !empty( $gtm_cat ) ) { print $gtm_cat[0]->cat_name; }?>',
'GTM_WP_Tags': '<?php if ( !empty( $posttags ) ) { print trim($gtm_tags); } ?>',
<?php } // Done with WordPress page type/conditions, you can add more default dataLayer variables below 
?>
'GTM_WP_dummy': 'Buckle your seatbelt Dorothy, because Kansas is going bye bye.'
});
// Don't forget to terminate your data layer correctly!
</script>