echo site_url() returns a different value than what is in the database siteurl field

Question

I have just copied a WordPress site to a different domain, everything on the front-end and admin side displays and works smoothly except I found my category links are linking to the old site domain. ( when echoed from get_category_link($parent->cat_ID) )

The siteurl and home fields in the database are correct (http://subdomain.newdomain.com)

However when I echo any of home_url() site_url() or network_site_url() I get http://www.oldsite.com

I've tried setting it in both the functions.php file and wp-config.php files, and have checked and re-checked the database field, even switching it away, breaking the site, switching it back to have the same results.

What is going on?

Answer 1

Looks like the previous developer had defined the site and home URLs in the main wp index.php file.