Add author and updated hatom data to posts and pages

functions.php

<?php
//Add hAtom data to all posts and pages
function sp_hatom_data($content) {
	$t = get_the_modified_time('F jS, Y');
	$author = get_the_author();
	$title = get_the_title();
	$content .= '<div class="hatom-extra" style="display:none;visibility:hidden;"><span class="entry-title">'.$title.'</span> was last modified: <span class="updated"> '.$t.'</span> by <span class="author vcard"><span class="fn">'.$author.'</span></span></div>';
	return $content;
}
add_filter('the_content', 'sp_hatom_data');