As I mentioned yesterday, I’m doing some work in WordPress right now, and a few minutes ago I tweeted that my custom code is messing with WP’s wp_get_archives() and wp_list_categories() functions, well, I found the problem.
I am including the 4RoadService.com header & utilities files in my WordPress theme, and I am using the same user here on my test server for both the main 4RoadService.com database and the WordPress database. It turns out that when the 4RoadService.com database connection was initialized, since it uses the same connection info as the WordPress database, the existing connection was just reused, (this behaviour, by the way, is well described in the PHP documentation), then when the 4RoadService.com connection was told to use the main 4RoadService database it did, thus switching our one and only connection away from the WordPress database, and making WordPress think that there were no posts on the blog.
Fortunately, there is a quick workaround, just add one more attribute to the mysql_connect() function so it looks like this:
$dblink = mysql_connect($host, $user, $pass, true);
This way a new connection is established, and the WordPress connection is left alone.
I am left wondering why, in the loop, WordPress was able to see my posts, perhaps it establishes a second database connection in there. However, I’m not going to spend the afternoon poking through the guts of WordPress.