I am running a site for a German NGO under the domain sub.example.org.
Recently, I added sub.example.ch for its Swiss spin-off.

Both (sub-)domains are pointing to the same physical location, a WP install (not multisite).

I have it setup such that sub.example.ch/register, for instance, will correctly show the content found under sub.example.org/register.

However, when a Swiss visitor surfs the site using regular on-site links, he or she will inevitably end up on the "regular" domain, since those utilize the "WordPress address" (or "site address") as defined in general settings, either via get_home_url or get_site_url() (or their less-deep get_bloginfo() equivalents).

Ideally, I'd like the visitor to keep surfing under the domain that he or she used to reach the site. Hence, I suppose I'd have to somehow filter the return value of the mentioned functions. A filter, which, as far as I know, does not exist.

  1. Does anybody have experience with this sort of thing and a decent solution handy?

  2. Is this maybe a dumb idea and I should let it go in the first place?

1 Answer 1


You could filter the option requests for the host.

In your wp-config.php below the line …

require_once ABSPATH . 'wp-settings.php';

… add the following lines:

add_filter( 'pre_option_home', 'set_current_host' );
add_filter( 'pre_option_siteurl', 'set_current_host' );

function set_current_host()
    return 'http://' . $_SERVER['HTTP_HOST'];

add_filter() is not available earlier, and you should keep such code in your wp-config.php. I don’t know if there are side effect or cases where it doesn’t work. Should not happen, but test it thoroughly.

  • I will test it thoroughly for sure. Now. Commented Apr 21, 2013 at 21:04
  • 4
    12 hours later: Works without exception. That the value would have to come from $_SERVER['HTTP_HOST'] is pretty straightforward, that would have been my approach too. While this was being answered, I was attempting to utilize the bloginfo_url filter from a plugin. Did not do the job. To put the filtering in the configuration file, however, I would have tried after days of contemplating only, if at all. The outcome of this solution surpassed my wildest expectations: Not only do links resolve nicely, login credentials work as well and even the back-end does not choke! Awesomeness! Commented Apr 22, 2013 at 9:14
  • 1
    Both (sub-)domains are pointing to the same physical location, a WP install (not multisite). Do do so, you need to log in your hosting service. When you create a subdomain, domain you have to specify a document root. Here, select the same path as your main Domain with WP installed on it. Then, add the code. Working perfectly, try to think about SEO ( canonical and alternate tags)
    – Romain
    Commented Oct 31, 2013 at 12:05

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