Accessing two databases wordpress

Question

I'm trying to access a second database with my wordpress system. To do this, I've attempted to follow the advice found here which seems to have worked for a lot of people.

In summary, I'm adding the following line to my functions.php:

global $newdb;
$newdb = new wpdb(DB_USER, DB_PASSWORD, DB_NAME, DB_HOST);
$newdb->show_errors();

Unfortunately, when I add this I come up with the following error:

Fatal error: Class 'wpdb' not found in /home/mine/www/wp-includes/functions.php

I'm sure I must be missing wrong (obviously, right?) but the instructions don't seem to have any extra steps that I've been leaving out.

Thanks for any help

Answer 1

When enhancing WordPress functionality, always use the theme's functions.php file (located, generally, in {WP root}/wp-content/themes/{your theme}/functions.php), or put your code into a plugin.

The rules for hacking core code are similar to the rules for optimization.

1. Don't do it.
2. (for experts only) Don't do it yet.

Answer 2

try something like this

add_action('init', 'doSomething');
function doSomething(){
     global $newdb;
     $newdb = new wpdb(DB_USER, DB_PASSWORD, DB_NAME, DB_HOST);
     $newdb->show_errors();
}