source: front-page-cats/trunk/front_page_cats.php @ 20923

<?php
/*
Plugin Name: Front Page Categories
Version: 0.3
Plugin URI: http://wordpress.org/#
Description: Select categories to display on the front page.
Author: Ryan Boren
*/ 

function fpc_where($where) {
  // Change this to the categories you want to show on the front page.
  // Example:  $cats_to_show = '1 2 3 4';
  $cats_to_show = '1';

        global $wpdb, $wp_query;

        if (! $wp_query->is_home) {
                return $where;
        }

        $cat = $cats_to_show;
        if (stristr($cat,'-')) {
                // Note: if we have a negative, we ignore all the positives. It must
                // always mean 'everything /except/ this one'. We should be able to do
                // multiple negatives but we don't :-(
                $eq = '!=';
                $andor = 'AND';
                $cat = explode('-',$cat);
                $cat = intval($cat[1]);
        } else {
                $eq = '=';
                $andor = 'OR';
        }

        $cat_array = explode(' ', $cat);
        $whichcat .= ' AND (category_id '.$eq.' '.intval($cat_array[0]);
        $whichcat .= get_category_children($cat_array[0], ' '.$andor.' category_id '.$eq.' ');
        for ($i = 1; $i < (count($cat_array)); $i = $i + 1) {
                $whichcat .= ' '.$andor.' category_id '.$eq.' '.intval($cat_array[$i]);
                $whichcat .= get_category_children($cat_array[$i], ' '.$andor.' category_id '.$eq.' ');
        }
        $whichcat .= ')';

        $where .= $whichcat;

  return $where;
}

function fpc_join($join) {
        global $wpdb, $wp_query;

        if (! $wp_query->is_home) {
                return $join;
        }

        $join .= " LEFT JOIN $wpdb->post2cat ON ($wpdb->posts.ID = $wpdb->post2cat.post_id) ";

  return $join;
}

add_filter('posts_join', 'fpc_join');
add_filter('posts_where', 'fpc_where');

?>