Old Way

require_once( $_SERVER['DOCUMENT_ROOT'] . '/wp-load.php' );

One problem with that solution is that it loads ALL the overhead of WordPress, which may be what you want if you need to use “The Loop” in your page, but usually isn’t what I’m looking for. If you’re using a caching plugin like W3TC to speed up your site, you’ll notice that including wp-load triggers W3TC to take over your page, which can give unexpected results. To work around this, I now set up the database using the few lines below.

New Way

define( 'BLOCK_LOAD', true );
require_once( $_SERVER['DOCUMENT_ROOT'] . '/wp-config.php' );
require_once( $_SERVER['DOCUMENT_ROOT'] . '/wp-includes/wp-db.php' );
$wpdb = new wpdb( DB_USER, DB_PASSWORD, DB_NAME, DB_HOST);

This does require one small change to the wp-config file to add support for blocking it from loading the rest of WordPress. You’ll need to find the line in the file that includes wp-settings and change it to look like the line below. In normal WordPress usage it will continue to include the wp-settings file as before, but in our special case, it will stop and only load the database settings.

if ( !( defined('BLOCK_LOAD') && BLOCK_LOAD ) ) require_once(ABSPATH . 'wp-settings.php');

NOTE: You may have to edit the paths above to reference the proper location of your WordPress install.

Wildcard DNS

The subdomain I tried was not an actual site for the client, but a wildcard DNS entry was sending it to the IP of the server anyways. If you have a wildcard entry set up for your domain(s) you should take care to see what your web server is serving up for subdomains you aren’t actually using. In most cases, it will serve up the default site for that IP address, but under whatever URL you used.

Fixing the issue

Once you know what site the server is serving up for your invalid subdomains, add or edit the .htaccess file for that site to include a redirect for any URLs not matching the correct domain. This way you’ll avoid any potential duplicate content issues and possible SEO penalties.

Option 1: Redirect any page requests to main website homepage

This option would send any visitors from http://subdomain.stormyfrog.com/awesome-page/ back to the homepage at http://www.stormyfrog.com/.

RewriteEngine on
RewriteCond %{HTTP_HOST} !www\.stormyfrog\.com [NC]
RewriteRule .* http://www.stormyfrog.com/ [R=301,L]

Option 2: Redirect page requests to equivalent page on correct domain

This option would send any visitors from http://subdomain.stormyfrog.com/awesome-page/ to http://www.stormyfrog.com/awesome-page/.

RewriteEngine on
RewriteCond %{HTTP_HOST} !www\.stormyfrog\.com [NC]
RewriteRule ^(.*)$ http://www.stormyfrog.com/$1 [R=301,L]

Option 3: Combined approach

This is the approach I personally use. Anyone entering the site with wwww (four w, a common mistake) or no www is redirected in a manner like Option 2 sending them to the right page. Anyone else making up subdomains or even using other domain names I may have pointing at the same IP but am not using would be sent to the homepage.

RewriteEngine on
RewriteCond %{HTTP_HOST} ^(wwww\.)?stormyfrog\.com [NC]
RewriteRule ^(.*)$ http://www.stormyfrog.com/$1 [R=301,L]
RewriteCond %{HTTP_HOST} !www\.stormyfrog\.com [NC]
RewriteRule .* http://www.stormyfrog.com/ [R=301,L]

Do you prefer no www for your site?

If you prefer your site running as http://stormyfrog.com/ rather than http://www.stormyfrog.com, use the variations below instead.

Option 1 for no-www

RewriteEngine on
RewriteCond %{HTTP_HOST} !^stormyfrog\.com [NC]
RewriteRule .* http://stormyfrog.com/ [R=301,L]

Option 2 for no-www

RewriteEngine on
RewriteCond %{HTTP_HOST} !^stormyfrog\.com [NC]
RewriteRule ^(.*)$ http://stormyfrog.com/$1 [R=301,L]

Option 3 for no-www

RewriteEngine on
RewriteCond %{HTTP_HOST} ^wwww?\.stormyfrog\.com [NC]
RewriteRule ^(.*)$ http://stormyfrog.com/$1 [R=301,L]
RewriteCond %{HTTP_HOST} !^stormyfrog\.com [NC]
RewriteRule .* http://stormyfrog.com/ [R=301,L]

Notes

This will only work on Apache-based web servers with security settings that permit you to override FileInfo settings in your htaccess file.