Using the Regular Expression to Replace External Links in WordPress for SEO purposes

wordpress-pad

Let’s say we want to put a REL=NOFOLLOW on all external links in your wordpress posts/pages, we can add a filter to parse the content using the regular expression replace function e.g. preg_replace_callback.

add_filter('the_content','add_utm_string',999);
function add_utm_string($content){
  $content = preg_replace_callback('~href\s*\=\s*[\'"](.*)[\'"]~i', function ($matches) {
     $home_url = parse_url(home_url())['host'];
     if (stripos($matches[1], $home_url) === false) {
        return 'href="'.$matches[1] . '?utm_source='. $home_url . '" rel=nofollow';
     }
     return 'href="'.$matches[1].'"';
  }, $content);
  return $content;
}

We add the filter function add_utm_string to the filter the_content. Then we use the PHP preg_replace_callback function that parses the HTML string of the current wordpress post/page, and replaces the hyperlink if it is external.

We use the following to extract the current domain name e.g. helloacm.com of your wordpress site.

$home_url = parse_url(home_url())['host'];

Then, we can exclude our own links. Otherwise, all external links will be added “NOFOLLOW” tag and the ?utm_source query parameter. You of course can customize the links building easily.

The PHP preg_replace_callback function takes the first parameter: Regular Expression Pattern, the second parameter is a call back function when pattern is matched, and the third paramter the original string.

This is a useful tweak for your wordpress template (you can add above PHP function to your theme template functions.php) that enhances your wordpress SEO.

Wordpress is King!

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• Using the Regular Expression to Replace External Links in Wordpress for SEO purposes
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–EOF (The Ultimate Computing & Technology Blog) —