WordPress/wp-includes/template-functions-category.php

<?php

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

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

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

	$categories = $category_cache[$id];

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

	return $categories;
}

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

	if ( empty($catlink) ) {
		$file = get_settings('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);
		$catlink = get_settings('home') . trailingslashit($catlink);
	}
	return apply_filters('category_link', $catlink, $category_id);
}

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 ) {
			$category->cat_name = $category->cat_name;
			$thelist .= "\n\t<li>";
			switch ( strtolower($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 ) {
			$category->cat_name = $category->cat_name;
			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 the_category($separator = '', $parents='') {
	echo get_the_category_list($separator, $parents);
}

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

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 )
		$chain .= get_category_parents($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_category_children($id, $before = '/', $after = '') {
	$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;
}

// Deprecated.
function the_category_ID($echo = true) {
	// Grab the first cat in the list.
	$categories = get_the_category();
	$cat = $categories[0]->cat_ID;

	if ( $echo )
		echo $cat;

	return $cat;
}

// Deprecated.
function the_category_head($before='', $after='') {
	global $currentcat, $previouscat;
	// Grab the first cat in the list.
	$categories = get_the_category();
	$currentcat = $categories[0]->category_id;
	if ( $currentcat != $previouscat ) {
		echo $before;
		echo get_the_category_by_ID($currentcat);
		echo $after;
		$previouscat = $currentcat;
	}
}

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);
}

// out of the WordPress loop
function dropdown_cats($optionall = 1, $all = 'All', $sort_column = 'ID', $sort_order = 'asc',
		$optiondates = 0, $optioncount = 0, $hide_empty = 1, $optionnone=FALSE,
		$selected=0, $hide=0) {
	global $wpdb;
	if ( ($file == 'blah') || ($file == '') )
		$file = get_settings('home') . '/';
	if ( !$selected )
		$selected=$cat;
	$sort_column = 'cat_'.$sort_column;

	$query = "
		SELECT cat_ID, cat_name, category_nicename,category_parent,
		COUNT($wpdb->post2cat.post_id) AS cat_count,
		DAYOFMONTH(MAX(post_date)) AS lastday, MONTH(MAX(post_date)) AS lastmonth
		FROM $wpdb->categories LEFT JOIN $wpdb->post2cat ON (cat_ID = category_id)
		LEFT JOIN $wpdb->posts ON (ID = post_id)
		WHERE cat_ID > 0
		";
	if ( $hide ) {
		$query .= " AND cat_ID != $hide";
		$query .= get_category_children($hide, " AND cat_ID != ");
	}
	$query .=" GROUP BY cat_ID";
	if ( intval($hide_empty) == 1 )
		$query .= " HAVING cat_count > 0";
	$query .= " ORDER BY $sort_column $sort_order, post_date DESC";

	$categories = $wpdb->get_results($query);
	echo "<select name='cat' class='postform'>\n";
	if ( intval($optionall) == 1 ) {
		$all = apply_filters('list_cats', $all);
		echo "\t<option value='0'>$all</option>\n";
	}
	if ( intval($optionnone) == 1 )
		echo "\t<option value='-1'>".__('None')."</option>\n";
	if ( $categories ) {
		foreach ( $categories as $category ) {
			$cat_name = apply_filters('list_cats', $category->cat_name, $category);
			echo "\t<option value=\"".$category->cat_ID."\"";
			if ( $category->cat_ID == $selected )
				echo ' selected="selected"';
			echo '>';
			echo $cat_name;
			if ( intval($optioncount) == 1 )
				echo '&nbsp;&nbsp;('.$category->cat_count.')';
			if ( intval($optiondates) == 1 )
				echo '&nbsp;&nbsp;'.$category->lastday.'/'.$category->lastmonth;
			echo "</option>\n";
		}
	}
	echo "</select>\n";
}

// out of the WordPress loop
function wp_list_cats($args = '') {
	parse_str($args, $r);
	if ( !isset($r['optionall']))
		$r['optionall'] = 0;
	if ( !isset($r['all']))
		$r['all'] = 'All';
	if ( !isset($r['sort_column']) )
		$r['sort_column'] = 'ID';
	if ( !isset($r['sort_order']) )
		$r['sort_order'] = 'asc';
	if ( !isset($r['file']) )
		$r['file'] = '';
	if ( !isset($r['list']) )
		$r['list'] = true;
	if ( !isset($r['optiondates']) )
		$r['optiondates'] = 0;
	if ( !isset($r['optioncount']) )
		$r['optioncount'] = 0;
	if ( !isset($r['hide_empty']) )
		$r['hide_empty'] = 1;
	if ( !isset($r['use_desc_for_title']) )
		$r['use_desc_for_title'] = 1;
	if ( !isset($r['children']) )
		$r['children'] = true;
	if ( !isset($r['child_of']) )
		$r['child_of'] = 0;
	if ( !isset($r['categories']) )
		$r['categories'] = 0;
	if ( !isset($r['recurse']) )
		$r['recurse'] = 0;
	if ( !isset($r['feed']) )
		$r['feed'] = '';
	if ( !isset($r['feed_image']) )
		$r['feed_image'] = '';
	if ( !isset($r['exclude']) )
		$r['exclude'] = '';
	if ( !isset($r['hierarchical']) )
		$r['hierarchical'] = true;

	return list_cats($r['optionall'], $r['all'], $r['sort_column'], $r['sort_order'], $r['file'],	$r['list'], $r['optiondates'], $r['optioncount'], $r['hide_empty'], $r['use_desc_for_title'], $r['children'], $r['child_of'], $r['categories'], $r['recurse'], $r['feed'], $r['feed_image'], $r['exclude'], $r['hierarchical']);
}

function list_cats($optionall = 1, $all = 'All', $sort_column = 'ID', $sort_order = 'asc', $file = '', $list = true, $optiondates = 0, $optioncount = 0, $hide_empty = 1, $use_desc_for_title = 1, $children=FALSE, $child_of=0, $categories=0, $recurse=0, $feed = '', $feed_image = '', $exclude = '', $hierarchical=FALSE) {
	global $wpdb, $wp_query;
	// Optiondates now works
	if ( '' == $file )
		$file = get_settings('home') . '/';

	$exclusions = '';
	if ( !empty($exclude) ) {
		$excats = preg_split('/[\s,]+/',$exclude);
		if ( count($excats) ) {
			foreach ( $excats as $excat ) {
				$exclusions .= ' AND cat_ID <> ' . intval($excat) . ' ';
			}
		}
	}

	$exclusions = apply_filters('list_cats_exclusions', $exclusions );

	if ( intval($categories) == 0 ) {
		$sort_column = 'cat_'.$sort_column;

		$query = "
			SELECT cat_ID, cat_name, category_nicename, category_description, category_parent, category_count
			FROM $wpdb->categories
			WHERE cat_ID > 0 $exclusions
			ORDER BY $sort_column $sort_order";

		$categories = $wpdb->get_results($query);
	}

	if ( $optiondates ) {
		$cat_dates = $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 $exclusions
		GROUP BY category_id");
		foreach ( $cat_dates as $cat_date ) {
			$category_timestamp["$cat_date->category_id"] = $cat_date->ts;
		}
	}

	$num_found=0;
	$thelist = "";

	foreach ( $categories as $category ) {
		if ( ( intval($hide_empty) == 0 || $category->category_count) && (!$hierarchical || $category->category_parent == $child_of) ) {
			$num_found++;
			$link = '<a href="'.get_category_link($category->cat_ID).'" ';
			if ( $use_desc_for_title == 0 || empty($category->category_description) )
				$link .= 'title="'. sprintf(__("View all posts filed under %s"), wp_specialchars($category->cat_name)) . '"';
			else
				$link .= 'title="' . wp_specialchars(apply_filters('category_description',$category->category_description,$category)) . '"';
			$link .= '>';
			$link .= apply_filters('list_cats', $category->cat_name, $category).'</a>';

			if ( (! empty($feed_image)) || (! empty($feed)) ) {

				$link .= ' ';

				if ( empty($feed_image) )
					$link .= '(';

				$link .= '<a href="' . get_category_rss_link(0, $category->cat_ID, $category->category_nicename) . '"';

				if ( !empty($feed) ) {
					$title = ' title="' . $feed . '"';
					$alt = ' alt="' . $feed . '"';
					$name = $feed;
					$link .= $title;
				}

				$link .= '>';

				if ( !empty($feed_image) )
					$link .= "<img src='$feed_image' $alt$title" . ' />';
				else
					$link .= $name;

				$link .= '</a>';

				if (empty($feed_image))
					$link .= ')';
			}

			if ( intval($optioncount) == 1 )
				$link .= ' ('.intval($category->category_count).')';

			if ( $optiondates ) {
				if ( $optiondates == 1 )
					$optiondates = 'Y-m-d';
				$link .= ' ' . gmdate($optiondates, $category_timestamp["$category->cat_ID"]);
			}

			if ( $list ) {
				$thelist .= "\t<li";
				if (($category->cat_ID == $wp_query->get_queried_object_id()) && is_category()) {
					$thelist .=  ' class="current-cat"';
				}
				$thelist .= ">$link\n";
			} else {
				$thelist .= "\t$link<br />\n";
			}

			if ($hierarchical && $children)
				$thelist .= list_cats($optionall, $all, $sort_column, $sort_order, $file, $list, $optiondates, $optioncount, $hide_empty, $use_desc_for_title, $hierarchical, $category->cat_ID, $categories, 1, $feed, $feed_image, $exclude, $hierarchical);
			if ($list)
				$thelist .= "</li>\n";
		}
	}
	if ( !$num_found && !$child_of ) {
		if ( $list ) {
			$before = '<li>';
			$after = '</li>';
		}
		echo $before . __("No categories") . $after . "\n";
		return;
	}
	if ( $list && $child_of && $num_found && $recurse ) {
		$pre = "\t\t<ul class='children'>";
		$post = "\t\t</ul>\n";
	} else {
		$pre = $post = '';
	}
	$thelist = $pre . $thelist . $post;
	if ( $recurse )
		return $thelist;
	echo apply_filters('list_cats', $thelist);
}

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

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

?>