Comments on: WordPress Hacking: Multiple Blogs On One Set of Tables

By: Jonathan Wise

Jonathan Wise — Fri, 01 Aug 2008 15:17:47 +0000

I can confirm that Tim’s modification works in 2.6

Another thing you might want to do is to make symlinks to folders in your main blog, so that your plugins and themes are available in your alternate blog…

Mario, that sounds like a righteous hack, but its definitely outside of the scope of this. Let us know if you crack it!

By: mario

mario — Tue, 29 Jul 2008 18:21:02 +0000

AAHHHHRRRGG!! I did everything as you said but it does not work.. Anyway…this is not even what I am trying to achieve but could have helped..what I am really trying to achieve is having one user dedicated admin installation with custom fields and all modified template pages sitting under a subdomain and my admin, full-capable admin installation wherever (on the main domain probably) while BOTH use the same tables and modify ONE website..thanks for the post though..

By: United States Of Martin » Blog Archive » One install to rule them all

United States Of Martin » Blog Archive » One install to rule them all — Thu, 08 May 2008 11:29:13 +0000

[...] like to disclose right away that almost everything in this post is lifted from this post and the comments therein. I only parrot it here with some supplementary info for the exact [...]

By: Jonathan Wise

Jonathan Wise — Sat, 19 Apr 2008 21:05:28 +0000

Awesome! Thanks for the update!

By: Tim

Tim — Fri, 18 Apr 2008 20:13:58 +0000

Jonathan - This was a brilliant help for me. I had a different issue (trying to create a blog for my dad and step-mom and a sub-blog for just my step-mom with the same database). Anyway, in Wordpress 2.5 you need to edit the wp-db.php file in the wp-includes directory. In the function set_prefix($prefix) section, you can override the settings. Following

foreach ( $this->tables as $table )
$this->$table = $this->prefix . $table;

the code should look like this:

$this->posts = ‘wp_’ . ‘posts’;
$this->users = ‘wp_’ . ‘users’;
$this->categories = ‘wp_’ . ‘categories’;
$this->post2cat = ‘wp_’ . ‘post2cat’;
$this->links = ‘wp_’ . ‘links’;
$this->postmeta = ‘wp_’ . ‘postmeta’;
$this->usermeta = ‘wp_’ . ‘usermeta’;
$this->terms = ‘wp_’ . ‘terms’;
$this->term_taxonomy = ‘wp_’ . ‘term_taxonomy’;
$this->term_relationships = ‘wp_’ . ‘term_relationships’;

Thanks again. This was a big help.

By: Jonathan Wise

Jonathan Wise — Mon, 14 Apr 2008 13:19:19 +0000

Try this: below the line $prefix = $wpdb->set_prefix($table_prefix);
just manually over-ride the other tables by adding this code:
$wpdb->users = ‘wp_’ . ‘users’; $wpdb->posts = ‘wp_’ . ‘posts’; $wpdb->comments = ‘wp_’ . ‘comments’

We let Wordpress do its global (once-for-all) setting, then we take over by repointing the tables we’re interested in. I’m not able to test this at the moment, but give it a try and let us know if it works!

By: Jonathan Wise

Jonathan Wise — Mon, 14 Apr 2008 13:16:20 +0000

The problem with the wp-settings.php file is that they’ve moved to a “set once for all” approach. The line $prefix = $wpdb->set_prefix($table_prefix); sets the table prefix for users, posts AND options, which prevents us from over-riding just the tables we want. I’ll keep poking…

By: Jonathan Wise

Jonathan Wise — Mon, 14 Apr 2008 13:07:42 +0000

For problem #1, it appears that wp-settings.php has changed significantly since 2.1. I’m not sure how to update these instructions to make them work. I’ll keep looking when I have some time.

For problem #2, try enclosing the newwp_user_level in quotes, so the command would look like this:
INSERT INTO wp_usermeta (user_id, meta_key, meta_value) VALUES (1, ‘newwp_user_level’, 10)

I used phpMySql to insert it by hand — I didn’t actually use a SQL statement, so I must have made an error when deriving the code for my post. I’ll update it.

Hope this helps! These instructions were originally written for WordPress 2.1, so if anyone knows how to change things for 2.5, let us know!

By: shamus

shamus — Fri, 11 Apr 2008 00:57:32 +0000

Hi, ran into issues during step 2, I did not find any of the mentioned lines in wp-settings.

I did find one line which looks similar:

$prefix = $wpdb->set_prefix($table_prefix);

but did not have success modifying it as mentioned in the link above, possible i am doing it wrong?

newwp_ is the custom code for the 2nd install on the same database, so i changed it to read:

$prefix = ‘newwp_’ . ‘posts’;

also, i get the following sql error when trying to add the admin user. here is my modified query and the error.

INSERT INTO wp_usermeta (user_id, meta_key, meta_value) VALUES (1, newwp_user_level, 10)

#1054 - Unknown column ‘newwp_user_level’ in ‘field list’

Default is wp_ and new is newwp_

Any help would be much appreciated.

By: Jonathan Wise

Jonathan Wise — Tue, 19 Feb 2008 16:56:57 +0000

You can run this with as many domains, subdomains or in-domain directories as you want… but this is really only a hack to get Wordpress installations to share a database.
I don’t know much about Wordpress MU, but I can tell you that this approach requires a Wordpress install for each site (regardless of domain name) you want to use.
In other words, you’d have at least one new table in your SQL database for each site, and you’d have one Wordpress folder on your server for each site. If you want to upgrade to a new version of Wordpress, you’d have to upgrade each installation. For what you’re trying to do, it seems like WordPress MU would be a better approach…