Adding WordPress.com Follow button to all posts

wpcomfollow-allposts.php

add_filter ('the_content', 'insertWPcomFollowerButton');
function insertWPcomFollowerButton($content) {
   if(is_single()) {
      $content.= '<a class="wordpress-follow-button" href="http://exoticmysticism.com" data-blog="http://exoticmysticism.com" data-lang="en">Follow Lisa Joy on WordPress.com</a>';
      $content.= '<script type="text/javascript">(function(d){var f = d.getElementsByTagName('SCRIPT')[0], p = d.createElement('SCRIPT');p.type = 'text/javascript';p.async = true;p.src = '//widgets.wp.com/platform.js';f.parentNode.insertBefore(p,f);}(document));</script>';
       }
   return $content;
}