Web browsers store a lot of information about how you navigate the internet, and one of those metrics is called a referrer. A referrer is the page that you were on before the page you are currently on. By checking this browser option we can eliminate quite a few of our spammy comments from bots that crawl the internet and post links to certain ‘medical solutions’.  Bellow is another WordPress PHP Snippet that you can post into your functions.php and will check whether a referrer exists or not.