To be able to pull data from custom tables in WordPress you’re almost always going to need some custom URL parameters to select the right data.  For example, let’s assume we are a company that sells widgets, and we have several types of widgets including “Blue Widgets” and “Red Widgets” and “Black Widgets”.  What we want from our new Amazing New WordPress Site is to display a page listing all of the types of widgets we sell and for users to be able to click on a link for each widget type and drill down and see more details on each type of widget.  The URL structure for such a site might look like this (in mod_rewrite permalink form):

http://www.our-site.com/widgets/
http://www.our-site.com/widgets/blue-widgets/
http://www.our-site.com/widgets/red-widgets/

To be able to pull the data for blue widgets from a custom MySQL table we must get some information from the URL the user is requesting. If your WordPress install is using mod_rewrite permalinks then this can be pulled from the URL by adding rewrite rules to WordPress. To do this you must have created a WordPress child theme. Once that is done open the child theme’s functions.php file and add the following code:

/*
* Add re-rewite rules for widget pages.  Remember to refresh permalinks if changing this
*/
function add_rewrite_rules($aRules) {
$aWidgetPage = array('widgets/([^/]+)/?$' => 'index.php?pagename=widget&widget_name=$matches[1]');
$aRules = $aWidgetPage + $aRules;
return $aRules;
}

// hook add_rewrite_rules function into rewrite_rules_array
add_filter('rewrite_rules_array', 'add_rewrite_rules');

The add_filter call allows us to add rules to the WordPress rewrite rule array. The function add_rewrite_rules adds the actual rewrite rule itself. Note that you must refresh WordPress permalinks after you’ve added this code for it to work correctly. Basically the rule we’ve added passes everything after the /widgets/ part of the URL as the URL parameter “widget_name” to a WordPress page called “widget”. The URL parameter will automatically be added to the WordPress query_vars array. Of course we’re going to have to create a WordPress page called “widget” and once we’ve done that the widget_name URL parameter is going to be available for use. You can access it via PHP (perhaps from a custom page template) using this code:

$widget_name='';
if(isset($wp_query->query_vars['widget_name'])) 
{
	$widget_name= urldecode($wp_query->query_vars['widget_name']);
}

Once you’ve read the widget_name parameter you can use it to access database information. Of course you’re going to need to make sure widget_name is unique in your database table. If it’s not you might like to consider embedding a database ID in your product links and parsing that out of the URL parameter. You could do that pretty simply by creating product links that look like this:

http://www.our-site.com/widgets/blue-widgets-1/
http://www.our-site.com/widgest/red-widgets-2/
http://www.our-site.com/widgest/purple-widgets-3/

And then exploding them out of the URL parameter like this:

$widget_name='';
if(isset($wp_query->query_vars['widget_name'])) 
{
	$widget_name= urldecode($wp_query->query_vars['widget_name']);
        $widget_array=explode("-",$widget_name);
        $widget_id=$widget_array[count($widget_array-1)];
}

Next post I’ll cover how to create the master list of widgets including pulling the records from a custom table putting that information in a ShortCode that can be used in any WordPress post or page.