how to add nofollow to external links in php

how to add nofollow to external links in php - try this code to add rel="nofollow" in all external links on your website, work correctly on PHP, Codeigniter, Laravel, Yii and etc.

in this case i use Codeigniter 3 and jQuery plugin

$("a:not(a[href^='<?=base_url()?>'],a[href^='javascript'],a[href^='#'])" ).attr({

            rel: "nofollow",

            target: "_blank"

          });

You can add it on footer.php, note : <?=base_url()?> can change to https://yourdomain.com

And then, test give <a> tag external links, and check on inspect element, there must be rel=nofollow and target _blank