root/tags/2.1/wp-includes/category.php

<?php

function get_all_category_ids() {
    global $wpdb;

    if ( ! $cat_ids = wp_cache_get('all_category_ids', 'category') ) {
        $cat_ids = $wpdb->get_col("SELECT cat_ID FROM $wpdb->categories");
        wp_cache_set('all_category_ids', $cat_ids, 'category');
    }

    return $cat_ids;
}

function &get_categories($args = '') {
    global $wpdb, $category_links;

    if ( is_array($args) )
        $r = &$args;
    else
        parse_str($args, $r);

    $defaults = array('type' => 'post', 'child_of' => 0, 'orderby' => 'name', 'order' => 'ASC',
        'hide_empty' => true, 'include_last_update_time' => false, 'hierarchical' => 1, 'exclude' => '', 'include' => '',
        'number' => '', 'pad_counts' => false);
    $r = array_merge($defaults, $r);
    if ( 'count' == $r['orderby'] )
        $r['orderby'] = 'category_count';
    else
        $r['orderby'] = "cat_" . $r['orderby'];  // restricts order by to cat_ID and cat_name fields
    $r['number'] = (int) $r['number'];
    extract($r);

    $key = md5( serialize( $r ) );
    if ( $cache = wp_cache_get( 'get_categories', 'category' ) )
        if ( isset( $cache[ $key ] ) )
            return $cache[ $key ];

    $where = 'cat_ID > 0';
    $inclusions = '';
    if ( !empty($include) ) {
        $child_of = 0; //ignore child_of and exclude params if using include
        $exclude = '';
        $incategories = preg_split('/[\s,]+/',$include);
        if ( count($incategories) ) {
            foreach ( $incategories as $incat ) {
                if (empty($inclusions))
                    $inclusions = ' AND ( cat_ID = ' . intval($incat) . ' ';
                else
                    $inclusions .= ' OR cat_ID = ' . intval($incat) . ' ';
            }
        }
    }
    if (!empty($inclusions))
        $inclusions .= ')';
    $where .= $inclusions;

    $exclusions = '';
    if ( !empty($exclude) ) {
        $excategories = preg_split('/[\s,]+/',$exclude);
        if ( count($excategories) ) {
            foreach ( $excategories as $excat ) {
                if (empty($exclusions))
                    $exclusions = ' AND ( cat_ID <> ' . intval($excat) . ' ';
                else
                    $exclusions .= ' AND cat_ID <> ' . intval($excat) . ' ';
                // TODO: Exclude children of excluded cats?   Note: children are getting excluded
            }
        }
    }
    if (!empty($exclusions))
        $exclusions .= ')';
    $exclusions = apply_filters('list_cats_exclusions', $exclusions, $r );
    $where .= $exclusions;

    if ( $hide_empty && !$hierarchical ) {
        if ( 'link' == $type )
            $where .= ' AND link_count > 0';
        else
            $where .= ' AND category_count > 0';
    }

    if ( !empty($number) )
        $number = 'LIMIT ' . $number;
    else
        $number = '';

    $categories = $wpdb->get_results("SELECT * FROM $wpdb->categories WHERE $where ORDER BY $orderby $order $number");

    if ( empty($categories) )
        return array();

    // TODO: Integrate this into the main query.
    if ( $include_last_update_time ) {
        $stamps = $wpdb->get_results("SELECT category_id, UNIX_TIMESTAMP( MAX(post_date) ) AS ts FROM $wpdb->posts, $wpdb->post2cat, $wpdb->categories
                            WHERE post_status = 'publish' AND post_id = ID AND $where GROUP BY category_id");
        global $cat_stamps;
        foreach ($stamps as $stamp)
            $cat_stamps[$stamp->category_id] = $stamp->ts;
        function stamp_cat($cat) {
            global $cat_stamps;
            $cat->last_update_timestamp = $cat_stamps[$cat->cat_ID];
            return $cat;
        }
        $categories = array_map('stamp_cat', $categories);
        unset($cat_stamps);
    }

    if ( $child_of || $hierarchical )
        $categories = & _get_cat_children($child_of, $categories);

    // Update category counts to include children.
    if ( $pad_counts )
        _pad_category_counts($type, $categories);

    // Make sure we show empty categories that have children.
    if ( $hierarchical && $hide_empty ) {
        foreach ( $categories as $k => $category ) {
            if ( ! $category->{'link' == $type ? 'link_count' : 'category_count'} ) {
                $children = _get_cat_children($category->cat_ID, $categories);
                foreach ( $children as $child )
                    if ( $child->{'link' == $type ? 'link_count' : 'category_count'} )
                        continue 2;

                // It really is empty
                unset($categories[$k]);
            }
        }
    }
    reset ( $categories );

    $cache[ $key ] = $categories;
    wp_cache_set( 'get_categories', $cache, 'category' );

    return apply_filters('get_categories', $categories, $r);
}

// Retrieves category data given a category ID or category object.
// Handles category caching.
function &get_category(&$category, $output = OBJECT) {
    global $wpdb;

    if ( empty($category) )
        return null;

    if ( is_object($category) ) {
        wp_cache_add($category->cat_ID, $category, 'category');
        $_category = $category;
    } else {
        if ( ! $_category = wp_cache_get($category, 'category') ) {
            $_category = $wpdb->get_row("SELECT * FROM $wpdb->categories WHERE cat_ID = '$category' LIMIT 1");
            wp_cache_set($category, $_category, 'category');
        }
    }

    $_category = apply_filters('get_category', $_category);

    if ( $output == OBJECT ) {
        return $_category;
    } elseif ( $output == ARRAY_A ) {
        return get_object_vars($_category);
    } elseif ( $output == ARRAY_N ) {
        return array_values(get_object_vars($_category));
    } else {
        return $_category;
    }
}

function get_category_by_path($category_path, $full_match = true, $output = OBJECT) {
    global $wpdb;
    $category_path = rawurlencode(urldecode($category_path));
    $category_path = str_replace('%2F', '/', $category_path);
    $category_path = str_replace('%20', ' ', $category_path);
    $category_paths = '/' . trim($category_path, '/');
    $leaf_path  = sanitize_title(basename($category_paths));
    $category_paths = explode('/', $category_paths);
    $full_path = '';
    foreach ( (array) $category_paths as $pathdir )
        $full_path .= ( $pathdir != '' ? '/' : '' ) . sanitize_title($pathdir);

    $categories = $wpdb->get_results("SELECT cat_ID, category_nicename, category_parent FROM $wpdb->categories WHERE category_nicename = '$leaf_path'");

    if ( empty($categories) )
        return NULL;

    foreach ($categories as $category) {
        $path = '/' . $leaf_path;
        $curcategory = $category;
        while ( ($curcategory->category_parent != 0) && ($curcategory->category_parent != $curcategory->cat_ID) ) {
            $curcategory = $wpdb->get_row("SELECT cat_ID, category_nicename, category_parent FROM $wpdb->categories WHERE cat_ID = '$curcategory->category_parent'");
            $path = '/' . $curcategory->category_nicename . $path;
        }

        if ( $path == $full_path )
            return get_category($category->cat_ID, $output);
    }

    // If full matching is not required, return the first cat that matches the leaf.
    if ( ! $full_match )
        return get_category($categories[0]->cat_ID, $output);

    return NULL;
}

// Get the ID of a category from its name
function get_cat_ID($cat_name='General') {
    global $wpdb;

    $cid = $wpdb->get_var("SELECT cat_ID FROM $wpdb->categories WHERE cat_name='$cat_name'");

    return $cid?$cid:1;    // default to cat 1
}

// Deprecate
function get_catname($cat_ID) {
    return get_cat_name($cat_ID);
}

// Get the name of a category from its ID
function get_cat_name($cat_id) {
    $cat_id = (int) $cat_id;
    $category = &get_category($cat_id);
    return $category->cat_name;
}

function cat_is_ancestor_of($cat1, $cat2) { 
    if ( is_int($cat1) ) 
        $cat1 = & get_category($cat1); 
    if ( is_int($cat2) ) 
        $cat2 = & get_category($cat2); 

    if ( !$cat1->cat_ID || !$cat2->category_parent ) 
        return false; 

    if ( $cat2->category_parent == $cat1->cat_ID ) 
        return true; 

    return cat_is_ancestor_of($cat1, get_category($cat2->parent_category)); 
} 

//
// Private
//

function &_get_cat_children($category_id, $categories) {
    if ( empty($categories) )
        return array();

    $category_list = array();
    foreach ( $categories as $category ) {
        if ( $category->cat_ID == $category_id )
            continue;

        if ( $category->category_parent == $category_id ) {
            $category_list[] = $category;
            if ( $children = _get_cat_children($category->cat_ID, $categories) )
                $category_list = array_merge($category_list, $children);
        }
    }

    return $category_list;
}

// Recalculates link or post counts by including items from child categories
// Assumes all relevant children are already in the $categories argument
function _pad_category_counts($type, &$categories) {
    global $wpdb;

    // Set up some useful arrays
    foreach ( $categories as $key => $cat ) {
        $cats[$cat->cat_ID] = & $categories[$key];
        $cat_IDs[] = $cat->cat_ID;
    }

    // Get the relevant post2cat or link2cat records and stick them in a lookup table
    if ( $type == 'post' ) {
        $results = $wpdb->get_results("SELECT post_id, category_id FROM $wpdb->post2cat LEFT JOIN $wpdb->posts ON post_id = ID WHERE category_id IN (".join(',', $cat_IDs).") AND post_type = 'post' AND post_status = 'publish'");
        foreach ( $results as $row )
            ++$cat_items[$row->category_id][$row->post_id];
    } else {
        $results = $wpdb->get_results("SELECT $wpdb->link2cat.link_id, category_id FROM $wpdb->link2cat LEFT JOIN $wpdb->links USING (link_id) WHERE category_id IN (".join(',', $cat_IDs).") AND link_visible = 'Y'");
        foreach ( $results as $row )
            ++$cat_items[$row->category_id][$row->link_id];
    }

    // Touch every ancestor's lookup row for each post in each category
    foreach ( $cat_IDs as $cat_ID ) {
        $child = $cat_ID;
        while ( $parent = $cats[$child]->category_parent ) {
            if ( !empty($cat_items[$cat_ID]) )
                foreach ( $cat_items[$cat_ID] as $item_id => $touches )
                    ++$cat_items[$parent][$item_id];
            $child = $parent;
        }
    }

    // Transfer the touched cells 
    foreach ( (array) $cat_items as $id => $items )
        if ( isset($cats[$id]) )
            $cats[$id]->{'link' == $type ? 'link_count' : 'category_count'} = count($items);
}

?>