Region category post

Below are the revised callbacks for pre_get_posts and post_link with fallback code in place. Replace what you currently have with these versions. In the tg_add_region() callback, I’ve assumed the IDs for the Benelux-News and International-News categories are 123 and 124 respectively. You must use the actual IDs in each line (that begins with if ( in_array(...) so that the proper location term can be assigned.

// Insert region into post links
add_filter('post_link', 'tg_add_region', 999, 3 );
function tg_add_region( $link, $post, $leavename) {
   global $region;
   $cats = wp_get_post_categories( $post->ID, array('fields'=>'ids',));
   if ( in_array( 123, $cats )) $region = 'benelux';
   if ( in_array( 124, $cats )) $region = 'international';
   if ( null == $region ) $region = 'international';
   $link = str_replace('.com/', ".com/$region/", $link );
   return $link;
}

// Add region category to main queries
add_action('pre_get_posts', 'tg_set_region');
function tg_set_region( $query ) {
  if ( get_option('page_on_front') == $query->get('page_id')) return;
  if ( !is_admin() && $query->is_main_query()) {
    global $region;
    $explode = explode('/', $_SERVER['REQUEST_URI']);
    $cat = $query->get('category_name');
    $region = $explode[1];
    if ( ! in_array( $region, array('benelux','international',))) $region = 'international';
    if ( '' != $cat ) $cat .= '+' . $region;
        else $cat = $region;
    $query->set('category_name', $cat);
  }
}

When inserting the region in post links, we try to use the assigned category to decide upon the region. In both the post_link and pre_get_posts callbacks, when all else fails in assigning the correct region, we use “international”.

Were any errors logged with that blank page? The code worked on my installation, which of course does not match yours, so compatibility issues have to be expected. If we can find out where the conflict is, the fall backs will work.