root/tags/2.1.1/wp-includes/category-template.php

<?php

function get_category_children($id, $before = '/', $after = '') {
    if ( 0 == $id )
        return '';

    $chain = '';

    $cat_ids = get_all_category_ids();
    foreach ( $cat_ids as $cat_id ) {
        if ( $cat_id == $id)
            continue;

        $category = get_category($cat_id);
        if ( $category->category_parent == $id ) {
            $chain .= $before.$category->cat_ID.$after;
            $chain .= get_category_children($category->cat_ID, $before, $after);
        }
    }
    return $chain;
}

function get_category_link($category_id) {
    global $wp_rewrite;
    $catlink = $wp_rewrite->get_category_permastruct();

    if ( empty($catlink) ) {
        $file = get_option('home') . '/';
        $catlink = $file . '?cat=' . $category_id;
    } else {
        $category = &get_category($category_id);
        $category_nicename = $category->category_nicename;

        if ( $parent = $category->category_parent )
            $category_nicename = get_category_parents($parent, false, '/', true) . $category_nicename . '/';

        $catlink = str_replace('%category%', $category_nicename, $catlink);
        $catlink = get_option('home') . trailingslashit($catlink);
    }
    return apply_filters('category_link', $catlink, $category_id);
}

function get_category_parents($id, $link = FALSE, $separator = '/', $nicename = FALSE){
    $chain = '';
    $parent = &get_category($id);

    if ( $nicename )
        $name = $parent->category_nicename;
    else
        $name = $parent->cat_name;

    if ( $parent->category_parent && ($parent->category_parent != $parent->cat_ID) )
        $chain .= get_category_parents($parent->category_parent, $link, $separator, $nicename);

    if ( $link )
        $chain .= '<a href="' . get_category_link($parent->cat_ID) . '" title="' . sprintf(__("View all posts in %s"), $parent->cat_name) . '">'.$name.'</a>' . $separator;
    else
        $chain .= $name.$separator;
    return $chain;
}

function get_the_category($id = false) {
global $post, $category_cache, $blog_id;

    if ( !$id )
        $id = $post->ID;

    if ( !isset($category_cache[$blog_id][$id]) )
        update_post_category_cache($id);

    $categories = $category_cache[$blog_id][$id];

    if ( !empty($categories) )
        sort($categories);
    else
        $categories = array();

    return $categories;
}

function get_the_category_by_ID($cat_ID) {
    $cat_ID = (int) $cat_ID;
    $category = &get_category($cat_ID);
    return $category->cat_name;
}

function get_the_category_list($separator = '', $parents='') {
    $categories = get_the_category();
    if (empty($categories))
        return apply_filters('the_category', __('Uncategorized'), $separator, $parents);

    $thelist = '';
    if ( '' == $separator ) {
        $thelist .= '<ul class="post-categories">';
        foreach ( $categories as $category ) {
            $thelist .= "\n\t<li>";
            switch ( strtolower($parents) ) {
                case 'multiple':
                    if ($category->category_parent)
                        $thelist .= get_category_parents($category->category_parent, TRUE);
                    $thelist .= '<a href="' . get_category_link($category->cat_ID) . '" title="' . sprintf(__("View all posts in %s"), $category->cat_name) . '" rel="category tag">'.$category->cat_name.'</a></li>';
                    break;
                case 'single':
                    $thelist .= '<a href="' . get_category_link($category->cat_ID) . '" title="' . sprintf(__("View all posts in %s"), $category->cat_name) . ' rel="category tag">';
                    if ($category->category_parent)
                        $thelist .= get_category_parents($category->category_parent, FALSE);
                    $thelist .= $category->cat_name.'</a></li>';
                    break;
                case '':
                default:
                    $thelist .= '<a href="' . get_category_link($category->cat_ID) . '" title="' . sprintf(__("View all posts in %s"), $category->cat_name) . '" rel="category tag">'.$category->cat_name.'</a></li>';
            }
        }
        $thelist .= '</ul>';
    } else {
        $i = 0;
        foreach ( $categories as $category ) {
            if ( 0 < $i )
                $thelist .= $separator . ' ';
            switch ( strtolower($parents) ) {
                case 'multiple':
                    if ( $category->category_parent )
                        $thelist .= get_category_parents($category->category_parent, TRUE);
                    $thelist .= '<a href="' . get_category_link($category->cat_ID) . '" title="' . sprintf(__("View all posts in %s"), $category->cat_name) . '" rel="category tag">'.$category->cat_name.'</a>';
                    break;
                case 'single':
                    $thelist .= '<a href="' . get_category_link($category->cat_ID) . '" title="' . sprintf(__("View all posts in %s"), $category->cat_name) . '" rel="category tag">';
                    if ( $category->category_parent )
                        $thelist .= get_category_parents($category->category_parent, FALSE);
                    $thelist .= "$category->cat_name</a>";
                    break;
                case '':
                default:
                    $thelist .= '<a href="' . get_category_link($category->cat_ID) . '" title="' . sprintf(__("View all posts in %s"), $category->cat_name) . '" rel="category tag">'.$category->cat_name.'</a>';
            }
            ++$i;
        }
    }
    return apply_filters('the_category', $thelist, $separator, $parents);
}

function in_category($category) { // Check if the current post is in the given category
    global $category_cache, $post, $blog_id;

    if ( isset( $category_cache[$blog_id][$post->ID][$category] ) )
        return true;
    else
        return false;
}

function the_category($separator = '', $parents='') {
    echo get_the_category_list($separator, $parents);
}

function category_description($category = 0) {
    global $cat;
    if ( !$category )
        $category = $cat;
    $category = & get_category($category);
    return apply_filters('category_description', $category->category_description, $category->cat_ID);
}

function wp_dropdown_categories($args = '') {
    if ( is_array($args) )
        $r = &$args;
    else
        parse_str($args, $r);

    $defaults = array('show_option_all' => '', 'show_option_none' => '', 'orderby' => 'ID',
        'order' => 'ASC', 'show_last_update' => 0, 'show_count' => 0,
        'hide_empty' => 1, 'child_of' => 0, 'exclude' => '', 'echo' => 1,
        'selected' => 0, 'hierarchical' => 0, 'name' => 'cat',
        'class' => 'postform');
    $defaults['selected'] = ( is_category() ) ? get_query_var('cat') : 0;
    $r = array_merge($defaults, $r);
    $r['include_last_update_time'] = $r['show_last_update'];
    extract($r);

    $categories = get_categories($r);

    $output = '';
    if ( ! empty($categories) ) {
        $output = "<select name='$name' id='$name' class='$class'>\n";

        if ( $show_option_all ) {
            $show_option_all = apply_filters('list_cats', $show_option_all);
            $output .= "\t<option value='0'>$show_option_all</option>\n";
        }

        if ( $show_option_none) {
            $show_option_none = apply_filters('list_cats', $show_option_none);
            $output .= "\t<option value='-1'>$show_option_none</option>\n";
        }

        if ( $hierarchical )
            $depth = 0;  // Walk the full depth.
        else
            $depth = -1; // Flat.

        $output .= walk_category_dropdown_tree($categories, $depth, $r);
        $output .= "</select>\n";
    }

    $output = apply_filters('wp_dropdown_cats', $output);

    if ( $echo )
        echo $output;

    return $output;
}

function wp_list_categories($args = '') {
    if ( is_array($args) )
        $r = &$args;
    else
        parse_str($args, $r);

    $defaults = array('show_option_all' => '', 'orderby' => 'name',
        'order' => 'ASC', 'show_last_update' => 0, 'style' => 'list',
        'show_count' => 0, 'hide_empty' => 1, 'use_desc_for_title' => 1,
        'child_of' => 0, 'feed' => '', 'feed_image' => '', 'exclude' => '',
        'hierarchical' => true, 'title_li' => __('Categories'));
    $r = array_merge($defaults, $r);
    if ( !isset($r['pad_counts']) && $r['show_count'] && $r['hierarchical'] )
        $r['pad_counts'] = true;
    if ( isset($r['show_date']) )
        $r['include_last_update_time'] = $r['show_date'];
    extract($r);

    $categories = get_categories($r);

    $output = '';
    if ( $title_li && 'list' == $style )
            $output = '<li class="categories">' . $r['title_li'] . '<ul>';

    if ( empty($categories) ) {
        if ( 'list' == $style )
            $output .= '<li>' . __("No categories") . '</li>';
        else
            $output .= __("No categories");
    } else {
        global $wp_query;
        
        if ( is_category() )
            $r['current_category'] = $wp_query->get_queried_object_id();

        if ( $hierarchical )
            $depth = 0;  // Walk the full depth.
        else
            $depth = -1; // Flat.

        $output .= walk_category_tree($categories, $depth, $r);
    }

    if ( $title_li && 'list' == $style )
        $output .= '</ul></li>';

    echo apply_filters('wp_list_categories', $output);
}

//
// Helper functions
//

function walk_category_tree() {
    $walker = new Walker_Category;
    $args = func_get_args();
    return call_user_func_array(array(&$walker, 'walk'), $args);
}

function walk_category_dropdown_tree() {
    $walker = new Walker_CategoryDropdown;
    $args = func_get_args();
    return call_user_func_array(array(&$walker, 'walk'), $args);
}

?>