WordPress/wp-includes/taxonomy.php

<?php
/**
 * Taxonomy API
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 */

//
// Taxonomy Registration
//

/**
 * Creates the initial taxonomies when 'init' action is fired.
 */
function create_initial_taxonomies() {
	register_taxonomy( 'category', 'post', array(
		'hierarchical' => true,
	 	'update_count_callback' => '_update_post_term_count',
		'query_var' => 'category_name',
		'rewrite' => array(
					'hierarchical' => true,
					'slug' => get_option('category_base') ? get_option('category_base') : 'category',
					'with_front' => false),
		'public' => true,
		'show_ui' => true,
		'_builtin' => true,
	) );

	register_taxonomy( 'post_tag', 'post', array(
	 	'hierarchical' => false,
		'update_count_callback' => '_update_post_term_count',
		'query_var' => 'tag',
		'rewrite' => array(
					'slug' => get_option('tag_base') ? get_option('tag_base') : 'tag' ,
					'with_front' => false),
		'public' => true,
		'show_ui' => true,
		'_builtin' => true,
	) );

	register_taxonomy( 'nav_menu', 'nav_menu_item', array(
		'public' => false,
		'hierarchical' => false,
		'labels' => array(
			'name' => __( 'Navigation Menus' ),
			'singular_name' => __( 'Navigation Menu' ),
		),
		'query_var' => false,
		'rewrite' => false,
		'show_ui' => false,
		'_builtin' => true,
		'show_in_nav_menus' => false,
	) ) ;

	register_taxonomy( 'link_category', 'link', array(
		'hierarchical' => false,
		'labels' => array(
			'name' => __( 'Link Categories' ),
			'singular_name' => __( 'Link Category' ),
			'search_items' => __( 'Search Link Categories' ),
			'popular_items' => null,
			'all_items' => __( 'All Link Categories' ),
			'edit_item' => __( 'Edit Link Category' ),
			'update_item' => __( 'Update Link Category' ),
			'add_new_item' => __( 'Add New Link Category' ),
			'new_item_name' => __( 'New Link Category Name' ),
			'separate_items_with_commas' => null,
			'add_or_remove_items' => null,
			'choose_from_most_used' => null,
		),
		'query_var' => false,
		'rewrite' => false,
		'public' => false,
		'show_ui' => false,
		'_builtin' => true,
	) ) ;

	register_taxonomy( 'post_format', 'post', array(
		'public' => false,
		'hierarchical' => false,
		'labels' => array(
			'name' => '',
			'singular_name' => '',
		),
		'query_var' => false,
		'rewrite' => false,
		'show_ui' => false,
		'_builtin' => true,
		'show_in_nav_menus' => false,
	) ) ;
}
add_action( 'init', 'create_initial_taxonomies', 0 ); // highest priority

/**
 * Get a list of registered taxonomy objects.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 3.0.0
 * @uses $wp_taxonomies
 * @see register_taxonomy
 *
 * @param array $args An array of key => value arguments to match against the taxonomy objects.
 * @param string $output The type of output to return, either taxonomy 'names' or 'objects'. 'names' is the default.
 * @param string $operator The logical operation to perform. 'or' means only one element
 *  from the array needs to match; 'and' means all elements must match. The default is 'and'.
 * @return array A list of taxonomy names or objects
 */
function get_taxonomies( $args = array(), $output = 'names', $operator = 'and' ) {
	global $wp_taxonomies;

	$field = ('names' == $output) ? 'name' : false;

	return wp_filter_object_list($wp_taxonomies, $args, $operator, $field);
}


/**
 * Return all of the taxonomy names that are of $object_type.
 *
 * It appears that this function can be used to find all of the names inside of
 * $wp_taxonomies global variable.
 *
 * <code><?php $taxonomies = get_object_taxonomies('post'); ?></code> Should
 * result in <code>Array('category', 'post_tag')</code>
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses $wp_taxonomies
 *
 * @param array|string|object $object Name of the type of taxonomy object, or an object (row from posts)
 * @param string $output The type of output to return, either taxonomy 'names' or 'objects'. 'names' is the default.
 * @return array The names of all taxonomy of $object_type.
 */
function get_object_taxonomies($object, $output = 'names') {
	global $wp_taxonomies;

	if ( is_object($object) ) {
		if ( $object->post_type == 'attachment' )
			return get_attachment_taxonomies($object);
		$object = $object->post_type;
	}

	$object = (array) $object;

	$taxonomies = array();
	foreach ( (array) $wp_taxonomies as $tax_name => $tax_obj ) {
		if ( array_intersect($object, (array) $tax_obj->object_type) ) {
			if ( 'names' == $output )
				$taxonomies[] = $tax_name;
			else
				$taxonomies[ $tax_name ] = $tax_obj;
		}
	}

	return $taxonomies;
}

/**
 * Retrieves the taxonomy object of $taxonomy.
 *
 * The get_taxonomy function will first check that the parameter string given
 * is a taxonomy object and if it is, it will return it.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses $wp_taxonomies
 * @uses taxonomy_exists() Checks whether taxonomy exists
 *
 * @param string $taxonomy Name of taxonomy object to return
 * @return object|bool The Taxonomy Object or false if $taxonomy doesn't exist
 */
function get_taxonomy( $taxonomy ) {
	global $wp_taxonomies;

	if ( ! taxonomy_exists( $taxonomy ) )
		return false;

	return $wp_taxonomies[$taxonomy];
}

/**
 * Checks that the taxonomy name exists.
 *
 * Formerly is_taxonomy(), introduced in 2.3.0.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 3.0.0
 *
 * @uses $wp_taxonomies
 *
 * @param string $taxonomy Name of taxonomy object
 * @return bool Whether the taxonomy exists.
 */
function taxonomy_exists( $taxonomy ) {
	global $wp_taxonomies;

	return isset( $wp_taxonomies[$taxonomy] );
}

/**
 * Whether the taxonomy object is hierarchical.
 *
 * Checks to make sure that the taxonomy is an object first. Then Gets the
 * object, and finally returns the hierarchical value in the object.
 *
 * A false return value might also mean that the taxonomy does not exist.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses taxonomy_exists() Checks whether taxonomy exists
 * @uses get_taxonomy() Used to get the taxonomy object
 *
 * @param string $taxonomy Name of taxonomy object
 * @return bool Whether the taxonomy is hierarchical
 */
function is_taxonomy_hierarchical($taxonomy) {
	if ( ! taxonomy_exists($taxonomy) )
		return false;

	$taxonomy = get_taxonomy($taxonomy);
	return $taxonomy->hierarchical;
}

/**
 * Create or modify a taxonomy object. Do not use before init.
 *
 * A simple function for creating or modifying a taxonomy object based on the
 * parameters given. The function will accept an array (third optional
 * parameter), along with strings for the taxonomy name and another string for
 * the object type.
 *
 * Nothing is returned, so expect error maybe or use taxonomy_exists() to check
 * whether taxonomy exists.
 *
 * Optional $args contents:
 *
 * label - Name of the taxonomy shown in the menu. Usually plural. If not set, labels['name'] will be used.
 *
 * hierarchical - has some defined purpose at other parts of the API and is a
 * boolean value.
 *
 * update_count_callback - works much like a hook, in that it will be called
 * when the count is updated.
 *
 * rewrite - false to prevent rewrite, or array('slug'=>$slug) to customize
 * permastruct; default will use $taxonomy as slug.
 *
 * query_var - false to prevent queries, or string to customize query var
 * (?$query_var=$term); default will use $taxonomy as query var.
 *
 * public - If the taxonomy should be publically queryable; //@TODO not implemented.
 * defaults to true.
 *
 * show_ui - If the WordPress UI admin tags UI should apply to this taxonomy;
 * defaults to public.
 *
 * show_in_nav_menus - true makes this taxonomy available for selection in navigation menus.
 * Defaults to public.
 *
 * show_tagcloud - false to prevent the taxonomy being listed in the Tag Cloud Widget;
 * defaults to show_ui which defalts to public.
 *
 * labels - An array of labels for this taxonomy. You can see accepted values in {@link get_taxonomy_labels()}. By default tag labels are used for non-hierarchical types and category labels for hierarchical ones.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 * @uses $wp_taxonomies Inserts new taxonomy object into the list
 * @uses $wp_rewrite Adds rewrite tags and permastructs
 * @uses $wp Adds query vars
 *
 * @param string $taxonomy Name of taxonomy object
 * @param array|string $object_type Name of the object type for the taxonomy object.
 * @param array|string $args See above description for the two keys values.
 */
function register_taxonomy( $taxonomy, $object_type, $args = array() ) {
	global $wp_taxonomies, $wp_rewrite, $wp;

	if ( ! is_array($wp_taxonomies) )
		$wp_taxonomies = array();

	$defaults = array(	'hierarchical' => false,
						'update_count_callback' => '',
						'rewrite' => true,
						'query_var' => $taxonomy,
						'public' => true,
						'show_ui' => null,
						'show_tagcloud' => null,
						'_builtin' => false,
						'labels' => array(),
						'capabilities' => array(),
						'show_in_nav_menus' => null,
					);
	$args = wp_parse_args($args, $defaults);

	if ( false !== $args['query_var'] && !empty($wp) ) {
		if ( true === $args['query_var'] )
			$args['query_var'] = $taxonomy;
		$args['query_var'] = sanitize_title_with_dashes($args['query_var']);
		$wp->add_query_var($args['query_var']);
	}

	if ( false !== $args['rewrite'] && '' != get_option('permalink_structure') && !empty($wp_rewrite) ) {
		$args['rewrite'] = wp_parse_args($args['rewrite'], array(
			'slug' => sanitize_title_with_dashes($taxonomy),
			'with_front' => true,
			'hierarchical' => false
		));

		if ( $args['hierarchical'] && $args['rewrite']['hierarchical'] )
			$tag = '(.+?)';
		else
			$tag = '([^/]+)';

		$wp_rewrite->add_rewrite_tag("%$taxonomy%", $tag, $args['query_var'] ? "{$args['query_var']}=" : "taxonomy=$taxonomy&term=");
		$wp_rewrite->add_permastruct($taxonomy, "{$args['rewrite']['slug']}/%$taxonomy%", $args['rewrite']['with_front']);
	}

	if ( is_null($args['show_ui']) )
		$args['show_ui'] = $args['public'];

	// Whether to show this type in nav-menus.php. Defaults to the setting for public.
	if ( null === $args['show_in_nav_menus'] )
		$args['show_in_nav_menus'] = $args['public'];

	if ( is_null($args['show_tagcloud']) )
		$args['show_tagcloud'] = $args['show_ui'];

	$default_caps = array(
		'manage_terms' => 'manage_categories',
		'edit_terms'   => 'manage_categories',
		'delete_terms' => 'manage_categories',
		'assign_terms' => 'edit_posts',
	);
	$args['cap'] = (object) array_merge( $default_caps, $args['capabilities'] );
	unset( $args['capabilities'] );

	$args['name'] = $taxonomy;
	$args['object_type'] = (array) $object_type;

	$args['labels'] = get_taxonomy_labels( (object) $args );
	$args['label'] = $args['labels']->name;

	$wp_taxonomies[$taxonomy] = (object) $args;

	// register callback handling for metabox
 	add_filter('wp_ajax_add-' . $taxonomy, '_wp_ajax_add_hierarchical_term');
}

/**
 * Builds an object with all taxonomy labels out of a taxonomy object
 *
 * Accepted keys of the label array in the taxonomy object:
 * - name - general name for the taxonomy, usually plural. The same as and overriden by $tax->label. Default is Post Tags/Categories
 * - singular_name - name for one object of this taxonomy. Default is Post Tag/Category
 * - search_items - Default is Search Tags/Search Categories
 * - popular_items - This string isn't used on hierarchical taxonomies. Default is Popular Tags
 * - all_items - Default is All Tags/All Categories
 * - parent_item - This string isn't used on non-hierarchical taxonomies. In hierarchical ones the default is Parent Category
 * - parent_item_colon - The same as <code>parent_item</code>, but with colon <code>:</code> in the end
 * - edit_item - Default is Edit Tag/Edit Category
 * - update_item - Default is Update Tag/Update Category
 * - add_new_item - Default is Add New Tag/Add New Category
 * - new_item_name - Default is New Tag Name/New Category Name
 * - separate_items_with_commas - This string isn't used on hierarchical taxonomies. Default is "Separate tags with commas," used in the meta box.
 * - add_or_remove_items - This string isn't used on hierarchical taxonomies. Default is "Add or remove tags," used in the meta box when JavaScript is disabled.
 * - choose_from_most_used - This string isn't used on hierarchical taxonomies. Default is "Choose from the most used tags," used in the meta box.
 *
 * Above, the first default value is for non-hierarchical taxonomies (like tags) and the second one is for hierarchical taxonomies (like categories.)
 *
 * @since 3.0.0
 * @param object $tax Taxonomy object
 * @return object object with all the labels as member variables
 */

function get_taxonomy_labels( $tax ) {
	if ( isset( $tax->helps ) && empty( $tax->labels['separate_items_with_commas'] ) )
		$tax->labels['separate_items_with_commas'] = $tax->helps;

	$nohier_vs_hier_defaults = array(
		'name' => array( _x( 'Post Tags', 'taxonomy general name' ), _x( 'Categories', 'taxonomy general name' ) ),
		'singular_name' => array( _x( 'Post Tag', 'taxonomy singular name' ), _x( 'Category', 'taxonomy singular name' ) ),
		'search_items' => array( __( 'Search Tags' ), __( 'Search Categories' ) ),
		'popular_items' => array( __( 'Popular Tags' ), null ),
		'all_items' => array( __( 'All Tags' ), __( 'All Categories' ) ),
		'parent_item' => array( null, __( 'Parent Category' ) ),
		'parent_item_colon' => array( null, __( 'Parent Category:' ) ),
		'edit_item' => array( __( 'Edit Tag' ), __( 'Edit Category' ) ),
		'update_item' => array( __( 'Update Tag' ), __( 'Update Category' ) ),
		'add_new_item' => array( __( 'Add New Tag' ), __( 'Add New Category' ) ),
		'new_item_name' => array( __( 'New Tag Name' ), __( 'New Category Name' ) ),
		'separate_items_with_commas' => array( __( 'Separate tags with commas' ), null ),
		'add_or_remove_items' => array( __( 'Add or remove tags' ), null ),
		'choose_from_most_used' => array( __( 'Choose from the most used tags' ), null ),
	);
	$nohier_vs_hier_defaults['menu_name'] = $nohier_vs_hier_defaults['name'];

	return _get_custom_object_labels( $tax, $nohier_vs_hier_defaults );
}

/**
 * Add an already registered taxonomy to an object type.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 3.0.0
 * @uses $wp_taxonomies Modifies taxonomy object
 *
 * @param string $taxonomy Name of taxonomy object
 * @param array|string $object_type Name of the object type
 * @return bool True if successful, false if not
 */
function register_taxonomy_for_object_type( $taxonomy, $object_type) {
	global $wp_taxonomies;

	if ( !isset($wp_taxonomies[$taxonomy]) )
		return false;

	if ( ! get_post_type_object($object_type) )
		return false;

	$wp_taxonomies[$taxonomy]->object_type[] = $object_type;

	return true;
}

//
// Term API
//

/**
 * Retrieve object_ids of valid taxonomy and term.
 *
 * The strings of $taxonomies must exist before this function will continue. On
 * failure of finding a valid taxonomy, it will return an WP_Error class, kind
 * of like Exceptions in PHP 5, except you can't catch them. Even so, you can
 * still test for the WP_Error class and get the error message.
 *
 * The $terms aren't checked the same as $taxonomies, but still need to exist
 * for $object_ids to be returned.
 *
 * It is possible to change the order that object_ids is returned by either
 * using PHP sort family functions or using the database by using $args with
 * either ASC or DESC array. The value should be in the key named 'order'.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses $wpdb
 * @uses wp_parse_args() Creates an array from string $args.
 *
 * @param int|array $term_ids Term id or array of term ids of terms that will be used
 * @param string|array $taxonomies String of taxonomy name or Array of string values of taxonomy names
 * @param array|string $args Change the order of the object_ids, either ASC or DESC
 * @return WP_Error|array If the taxonomy does not exist, then WP_Error will be returned. On success
 *	the array can be empty meaning that there are no $object_ids found or it will return the $object_ids found.
 */
function get_objects_in_term( $term_ids, $taxonomies, $args = array() ) {
	global $wpdb;

	if ( ! is_array( $term_ids ) )
		$term_ids = array( $term_ids );

	if ( ! is_array( $taxonomies ) )
		$taxonomies = array( $taxonomies );

	foreach ( (array) $taxonomies as $taxonomy ) {
		if ( ! taxonomy_exists( $taxonomy ) )
			return new WP_Error( 'invalid_taxonomy', __( 'Invalid Taxonomy' ) );
	}

	$defaults = array( 'order' => 'ASC' );
	$args = wp_parse_args( $args, $defaults );
	extract( $args, EXTR_SKIP );

	$order = ( 'desc' == strtolower( $order ) ) ? 'DESC' : 'ASC';

	$term_ids = array_map('intval', $term_ids );

	$taxonomies = "'" . implode( "', '", $taxonomies ) . "'";
	$term_ids = "'" . implode( "', '", $term_ids ) . "'";

	$object_ids = $wpdb->get_col("SELECT tr.object_id FROM $wpdb->term_relationships AS tr INNER JOIN $wpdb->term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tt.taxonomy IN ($taxonomies) AND tt.term_id IN ($term_ids) ORDER BY tr.object_id $order");

	if ( ! $object_ids )
		return array();

	return $object_ids;
}

/*
 * Given a taxonomy query, generates SQL to be appended to a main query
 *
 * @since 3.1.0
 *
 * @param array $tax_query List of taxonomy queries. A single taxonomy query is an associative array:
 * - 'taxonomy' string|array The taxonomy being queried
 * - 'terms' string|array The list of terms
 * - 'field' string (optional) Which term field is being used.
 *		Possible values: 'term_id', 'slug' or 'name'
 *		Default: 'term_id'
 * - 'operator' string (optional)
 *		Possible values: 'IN' and 'NOT IN'.
 *		Default: 'IN'
 * - 'include_children' bool (optional) Whether to include child terms.
 *		Default: true
 *
 * @param string $primary_table
 * @param string $primary_id_column
 * @return array
 */
function get_tax_sql( $tax_query, $primary_table, $primary_id_column ) {
	global $wpdb;

	$join = '';
	$where = array();
	$i = 0;

	if ( isset( $tax_query['relation'] ) && strtoupper( $tax_query['relation'] ) == 'OR' ) {
		$relation = 'OR';
	} else {
		$relation = 'AND';
	}

	foreach ( $tax_query as $query ) {
		if ( ! is_array( $query ) )
			continue;

		extract( wp_parse_args( $query, array(
			'taxonomy' => array(),
			'terms' => array(),
			'include_children' => true,
			'field' => 'term_id',
			'operator' => 'IN',
		) ) );

		$taxonomies = (array) $taxonomy;

		foreach ( $taxonomies as $taxonomy ) {
			if ( ! taxonomy_exists( $taxonomy ) )
				return array( 'join' => '', 'where' => ' AND 0 = 1');
		}

		$taxonomies = "'" . implode( "', '", $taxonomies ) . "'";

		$terms = array_unique( (array) $terms );

		if ( empty( $terms ) )
			continue;

		if ( is_taxonomy_hierarchical( $taxonomy ) && $include_children ) {
			_transform_terms( $terms, $taxonomies, $field, 'term_id' );

			$children = array();
			foreach ( $terms as $term ) {
				$children = array_merge( $children, get_term_children( $term, $taxonomy ) );
				$children[] = $term;
			}
			$terms = $children;

			_transform_terms( $terms, $taxonomies, 'term_id', 'term_taxonomy_id' );
		}
		else {
			_transform_terms( $terms, $taxonomies, $field, 'term_taxonomy_id' );
		}

		if ( 'IN' == $operator ) {

			if ( empty( $terms ) ) {
				if ( 'OR' == $relation )
					continue;
				else
					return array( 'join' => '', 'where' => ' AND 0 = 1' );
			}

			$terms = implode( ',', $terms );

			$alias = $i ? 'tt' . $i : $wpdb->term_relationships;

			$join .= " INNER JOIN $wpdb->term_relationships";
			$join .= $i ? " AS $alias" : '';
			$join .= " ON ($primary_table.$primary_id_column = $alias.object_id)";

			$where[] = "$alias.term_taxonomy_id $operator ($terms)";
		}
		elseif ( 'NOT IN' == $operator ) {

			if ( empty( $terms ) )
				continue;

			$terms = implode( ',', $terms );

			$where[] = "$primary_table.$primary_id_column NOT IN (
				SELECT object_id
				FROM $wpdb->term_relationships
				WHERE term_taxonomy_id IN ($terms)
			)";
		}

		$i++;
	}

	if ( !empty( $where ) )
		$where = ' AND ( ' . implode( " $relation ", $where ) . ' )';
	else
		$where = '';

	return compact( 'join', 'where' );
}

function _transform_terms( &$terms, $taxonomies, $field, $resulting_field ) {
	global $wpdb;

	if ( empty( $terms ) )
		return;

	if ( $field == $resulting_field )
		return;

	$resulting_field = esc_sql( $resulting_field );

	switch ( $field ) {
		case 'slug':
		case 'name':
			$terms = "'" . implode( "','", array_map( 'sanitize_title_for_query', $terms ) ) . "'";
			$terms = $wpdb->get_col( "
				SELECT $wpdb->term_taxonomy.$resulting_field
				FROM $wpdb->term_taxonomy
				INNER JOIN $wpdb->terms USING (term_id)
				WHERE taxonomy IN ($taxonomies)
				AND $wpdb->terms.$field IN ($terms)
			" );
			break;

		default:
			$terms = implode( ',', array_map( 'intval', $terms ) );
			$terms = $wpdb->get_col( "
				SELECT $resulting_field
				FROM $wpdb->term_taxonomy
				WHERE taxonomy IN ($taxonomies)
				AND term_id IN ($terms)
			" );
	}
}

/**
 * Get all Term data from database by Term ID.
 *
 * The usage of the get_term function is to apply filters to a term object. It
 * is possible to get a term object from the database before applying the
 * filters.
 *
 * $term ID must be part of $taxonomy, to get from the database. Failure, might
 * be able to be captured by the hooks. Failure would be the same value as $wpdb
 * returns for the get_row method.
 *
 * There are two hooks, one is specifically for each term, named 'get_term', and
 * the second is for the taxonomy name, 'term_$taxonomy'. Both hooks gets the
 * term object, and the taxonomy name as parameters. Both hooks are expected to
 * return a Term object.
 *
 * 'get_term' hook - Takes two parameters the term Object and the taxonomy name.
 * Must return term object. Used in get_term() as a catch-all filter for every
 * $term.
 *
 * 'get_$taxonomy' hook - Takes two parameters the term Object and the taxonomy
 * name. Must return term object. $taxonomy will be the taxonomy name, so for
 * example, if 'category', it would be 'get_category' as the filter name. Useful
 * for custom taxonomies or plugging into default taxonomies.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses $wpdb
 * @uses sanitize_term() Cleanses the term based on $filter context before returning.
 * @see sanitize_term_field() The $context param lists the available values for get_term_by() $filter param.
 *
 * @param int|object $term If integer, will get from database. If object will apply filters and return $term.
 * @param string $taxonomy Taxonomy name that $term is part of.
 * @param string $output Constant OBJECT, ARRAY_A, or ARRAY_N
 * @param string $filter Optional, default is raw or no WordPress defined filter will applied.
 * @return mixed|null|WP_Error Term Row from database. Will return null if $term is empty. If taxonomy does not
 * exist then WP_Error will be returned.
 */
function &get_term($term, $taxonomy, $output = OBJECT, $filter = 'raw') {
	global $wpdb;
	$null = null;

	if ( empty($term) ) {
		$error = new WP_Error('invalid_term', __('Empty Term'));
		return $error;
	}

	if ( ! taxonomy_exists($taxonomy) ) {
		$error = new WP_Error('invalid_taxonomy', __('Invalid Taxonomy'));
		return $error;
	}

	if ( is_object($term) && empty($term->filter) ) {
		wp_cache_add($term->term_id, $term, $taxonomy);
		$_term = $term;
	} else {
		if ( is_object($term) )
			$term = $term->term_id;
		$term = (int) $term;
		if ( ! $_term = wp_cache_get($term, $taxonomy) ) {
			$_term = $wpdb->get_row( $wpdb->prepare( "SELECT t.*, tt.* FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id WHERE tt.taxonomy = %s AND t.term_id = %s LIMIT 1", $taxonomy, $term) );
			if ( ! $_term )
				return $null;
			wp_cache_add($term, $_term, $taxonomy);
		}
	}

	$_term = apply_filters('get_term', $_term, $taxonomy);
	$_term = apply_filters("get_$taxonomy", $_term, $taxonomy);
	$_term = sanitize_term($_term, $taxonomy, $filter);

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

/**
 * Get all Term data from database by Term field and data.
 *
 * Warning: $value is not escaped for 'name' $field. You must do it yourself, if
 * required.
 *
 * The default $field is 'id', therefore it is possible to also use null for
 * field, but not recommended that you do so.
 *
 * If $value does not exist, the return value will be false. If $taxonomy exists
 * and $field and $value combinations exist, the Term will be returned.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses $wpdb
 * @uses sanitize_term() Cleanses the term based on $filter context before returning.
 * @see sanitize_term_field() The $context param lists the available values for get_term_by() $filter param.
 *
 * @param string $field Either 'slug', 'name', or 'id'
 * @param string|int $value Search for this term value
 * @param string $taxonomy Taxonomy Name
 * @param string $output Constant OBJECT, ARRAY_A, or ARRAY_N
 * @param string $filter Optional, default is raw or no WordPress defined filter will applied.
 * @return mixed Term Row from database. Will return false if $taxonomy does not exist or $term was not found.
 */
function get_term_by($field, $value, $taxonomy, $output = OBJECT, $filter = 'raw') {
	global $wpdb;

	if ( ! taxonomy_exists($taxonomy) )
		return false;

	if ( 'slug' == $field ) {
		$field = 't.slug';
		$value = sanitize_title($value);
		if ( empty($value) )
			return false;
	} else if ( 'name' == $field ) {
		// Assume already escaped
		$value = stripslashes($value);
		$field = 't.name';
	} else {
		return get_term( (int) $value, $taxonomy, $output, $filter);
	}

	$term = $wpdb->get_row( $wpdb->prepare( "SELECT t.*, tt.* FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id WHERE tt.taxonomy = %s AND $field = %s LIMIT 1", $taxonomy, $value) );
	if ( !$term )
		return false;

	wp_cache_add($term->term_id, $term, $taxonomy);

	$term = apply_filters('get_term', $term, $taxonomy);
	$term = apply_filters("get_$taxonomy", $term, $taxonomy);
	$term = sanitize_term($term, $taxonomy, $filter);

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

/**
 * Merge all term children into a single array of their IDs.
 *
 * This recursive function will merge all of the children of $term into the same
 * array of term IDs. Only useful for taxonomies which are hierarchical.
 *
 * Will return an empty array if $term does not exist in $taxonomy.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses $wpdb
 * @uses _get_term_hierarchy()
 * @uses get_term_children() Used to get the children of both $taxonomy and the parent $term
 *
 * @param string $term_id ID of Term to get children
 * @param string $taxonomy Taxonomy Name
 * @return array|WP_Error List of Term Objects. WP_Error returned if $taxonomy does not exist
 */
function get_term_children( $term_id, $taxonomy ) {
	if ( ! taxonomy_exists($taxonomy) )
		return new WP_Error('invalid_taxonomy', __('Invalid Taxonomy'));

	$term_id = intval( $term_id );

	$terms = _get_term_hierarchy($taxonomy);

	if ( ! isset($terms[$term_id]) )
		return array();

	$children = $terms[$term_id];

	foreach ( (array) $terms[$term_id] as $child ) {
		if ( isset($terms[$child]) )
			$children = array_merge($children, get_term_children($child, $taxonomy));
	}

	return $children;
}

/**
 * Get sanitized Term field.
 *
 * Does checks for $term, based on the $taxonomy. The function is for contextual
 * reasons and for simplicity of usage. See sanitize_term_field() for more
 * information.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses sanitize_term_field() Passes the return value in sanitize_term_field on success.
 *
 * @param string $field Term field to fetch
 * @param int $term Term ID
 * @param string $taxonomy Taxonomy Name
 * @param string $context Optional, default is display. Look at sanitize_term_field() for available options.
 * @return mixed Will return an empty string if $term is not an object or if $field is not set in $term.
 */
function get_term_field( $field, $term, $taxonomy, $context = 'display' ) {
	$term = (int) $term;
	$term = get_term( $term, $taxonomy );
	if ( is_wp_error($term) )
		return $term;

	if ( !is_object($term) )
		return '';

	if ( !isset($term->$field) )
		return '';

	return sanitize_term_field($field, $term->$field, $term->term_id, $taxonomy, $context);
}

/**
 * Sanitizes Term for editing.
 *
 * Return value is sanitize_term() and usage is for sanitizing the term for
 * editing. Function is for contextual and simplicity.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses sanitize_term() Passes the return value on success
 *
 * @param int|object $id Term ID or Object
 * @param string $taxonomy Taxonomy Name
 * @return mixed|null|WP_Error Will return empty string if $term is not an object.
 */
function get_term_to_edit( $id, $taxonomy ) {
	$term = get_term( $id, $taxonomy );

	if ( is_wp_error($term) )
		return $term;

	if ( !is_object($term) )
		return '';

	return sanitize_term($term, $taxonomy, 'edit');
}

/**
 * Retrieve the terms in a given taxonomy or list of taxonomies.
 *
 * You can fully inject any customizations to the query before it is sent, as
 * well as control the output with a filter.
 *
 * The 'get_terms' filter will be called when the cache has the term and will
 * pass the found term along with the array of $taxonomies and array of $args.
 * This filter is also called before the array of terms is passed and will pass
 * the array of terms, along with the $taxonomies and $args.
 *
 * The 'list_terms_exclusions' filter passes the compiled exclusions along with
 * the $args.
 *
 * The 'get_terms_orderby' filter passes the ORDER BY clause for the query
 * along with the $args array.
 *
 * The 'get_terms_fields' filter passes the fields for the SELECT query
 * along with the $args array.
 *
 * The list of arguments that $args can contain, which will overwrite the defaults:
 *
 * orderby - Default is 'name'. Can be name, count, term_group, slug or nothing
 * (will use term_id), Passing a custom value other than these will cause it to
 * order based on the custom value.
 *
 * order - Default is ASC. Can use DESC.
 *
 * hide_empty - Default is true. Will not return empty terms, which means
 * terms whose count is 0 according to the given taxonomy.
 *
 * exclude - Default is an empty array.  An array, comma- or space-delimited string
 * of term ids to exclude from the return array.  If 'include' is non-empty,
 * 'exclude' is ignored.
 *
 * exclude_tree - Default is an empty array.  An array, comma- or space-delimited
 * string of term ids to exclude from the return array, along with all of their
 * descendant terms according to the primary taxonomy.  If 'include' is non-empty,
 * 'exclude_tree' is ignored.
 *
 * include - Default is an empty array.  An array, comma- or space-delimited string
 * of term ids to include in the return array.
 *
 * number - The maximum number of terms to return.  Default is to return them all.
 *
 * offset - The number by which to offset the terms query.
 *
 * fields - Default is 'all', which returns an array of term objects.
 * If 'fields' is 'ids' or 'names', returns an array of
 * integers or strings, respectively.
 *
 * slug - Returns terms whose "slug" matches this value. Default is empty string.
 *
 * hierarchical - Whether to include terms that have non-empty descendants
 * (even if 'hide_empty' is set to true).
 *
 * search - Returned terms' names will contain the value of 'search',
 * case-insensitive.  Default is an empty string.
 *
 * name__like - Returned terms' names will begin with the value of 'name__like',
 * case-insensitive. Default is empty string.
 *
 * The argument 'pad_counts', if set to true will include the quantity of a term's
 * children in the quantity of each term's "count" object variable.
 *
 * The 'get' argument, if set to 'all' instead of its default empty string,
 * returns terms regardless of ancestry or whether the terms are empty.
 *
 * The 'child_of' argument, when used, should be set to the integer of a term ID.  Its default
 * is 0.  If set to a non-zero value, all returned terms will be descendants
 * of that term according to the given taxonomy.  Hence 'child_of' is set to 0
 * if more than one taxonomy is passed in $taxonomies, because multiple taxonomies
 * make term ancestry ambiguous.
 *
 * The 'parent' argument, when used, should be set to the integer of a term ID.  Its default is
 * the empty string '', which has a different meaning from the integer 0.
 * If set to an integer value, all returned terms will have as an immediate
 * ancestor the term whose ID is specified by that integer according to the given taxonomy.
 * The 'parent' argument is different from 'child_of' in that a term X is considered a 'parent'
 * of term Y only if term X is the father of term Y, not its grandfather or great-grandfather, etc.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses $wpdb
 * @uses wp_parse_args() Merges the defaults with those defined by $args and allows for strings.
 *
 * @param string|array $taxonomies Taxonomy name or list of Taxonomy names
 * @param string|array $args The values of what to search for when returning terms
 * @return array|WP_Error List of Term Objects and their children. Will return WP_Error, if any of $taxonomies do not exist.
 */
function &get_terms($taxonomies, $args = '') {
	global $wpdb;
	$empty_array = array();

	$single_taxonomy = false;
	if ( !is_array($taxonomies) ) {
		$single_taxonomy = true;
		$taxonomies = array($taxonomies);
	}

	foreach ( $taxonomies as $taxonomy ) {
		if ( ! taxonomy_exists($taxonomy) ) {
			$error = & new WP_Error('invalid_taxonomy', __('Invalid Taxonomy'));
			return $error;
		}
	}

	$defaults = array('orderby' => 'name', 'order' => 'ASC',
		'hide_empty' => true, 'exclude' => array(), 'exclude_tree' => array(), 'include' => array(),
		'number' => '', 'fields' => 'all', 'slug' => '', 'parent' => '',
		'hierarchical' => true, 'child_of' => 0, 'get' => '', 'name__like' => '',
		'pad_counts' => false, 'offset' => '', 'search' => '');
	$args = wp_parse_args( $args, $defaults );
	$args['number'] = absint( $args['number'] );
	$args['offset'] = absint( $args['offset'] );
	if ( !$single_taxonomy || !is_taxonomy_hierarchical($taxonomies[0]) ||
		'' !== $args['parent'] ) {
		$args['child_of'] = 0;
		$args['hierarchical'] = false;
		$args['pad_counts'] = false;
	}

	if ( 'all' == $args['get'] ) {
		$args['child_of'] = 0;
		$args['hide_empty'] = 0;
		$args['hierarchical'] = false;
		$args['pad_counts'] = false;
	}

	$args = apply_filters( 'get_terms_args', $args, $taxonomies );

	extract($args, EXTR_SKIP);

	if ( $child_of ) {
		$hierarchy = _get_term_hierarchy($taxonomies[0]);
		if ( !isset($hierarchy[$child_of]) )
			return $empty_array;
	}

	if ( $parent ) {
		$hierarchy = _get_term_hierarchy($taxonomies[0]);
		if ( !isset($hierarchy[$parent]) )
			return $empty_array;
	}

	// $args can be whatever, only use the args defined in defaults to compute the key
	$filter_key = ( has_filter('list_terms_exclusions') ) ? serialize($GLOBALS['wp_filter']['list_terms_exclusions']) : '';
	$key = md5( serialize( compact(array_keys($defaults)) ) . serialize( $taxonomies ) . $filter_key );
	$last_changed = wp_cache_get('last_changed', 'terms');
	if ( !$last_changed ) {
		$last_changed = time();
		wp_cache_set('last_changed', $last_changed, 'terms');
	}
	$cache_key = "get_terms:$key:$last_changed";
	$cache = wp_cache_get( $cache_key, 'terms' );
	if ( false !== $cache ) {
		$cache = apply_filters('get_terms', $cache, $taxonomies, $args);
		return $cache;
	}

	$_orderby = strtolower($orderby);
	if ( 'count' == $_orderby )
		$orderby = 'tt.count';
	else if ( 'name' == $_orderby )
		$orderby = 't.name';
	else if ( 'slug' == $_orderby )
		$orderby = 't.slug';
	else if ( 'term_group' == $_orderby )
		$orderby = 't.term_group';
	else if ( 'none' == $_orderby )
		$orderby = '';
	elseif ( empty($_orderby) || 'id' == $_orderby )
		$orderby = 't.term_id';

	$orderby = apply_filters( 'get_terms_orderby', $orderby, $args );

	if ( !empty($orderby) )
		$orderby = "ORDER BY $orderby";
	else
		$order = '';

	$where = "tt.taxonomy IN ('" . implode("', '", $taxonomies) . "')";
	$inclusions = '';
	if ( !empty($include) ) {
		$exclude = '';
		$exclude_tree = '';
		$interms = wp_parse_id_list($include);
		foreach ( $interms as $interm ) {
			if ( empty($inclusions) )
				$inclusions = ' AND ( t.term_id = ' . intval($interm) . ' ';
			else
				$inclusions .= ' OR t.term_id = ' . intval($interm) . ' ';
		}
	}

	if ( !empty($inclusions) )
		$inclusions .= ')';
	$where .= $inclusions;

	$exclusions = '';
	if ( !empty( $exclude_tree ) ) {
		$excluded_trunks = wp_parse_id_list($exclude_tree);
		foreach ( $excluded_trunks as $extrunk ) {
			$excluded_children = (array) get_terms($taxonomies[0], array('child_of' => intval($extrunk), 'fields' => 'ids', 'hide_empty' => 0));
			$excluded_children[] = $extrunk;
			foreach( $excluded_children as $exterm ) {
				if ( empty($exclusions) )
					$exclusions = ' AND ( t.term_id <> ' . intval($exterm) . ' ';
				else
					$exclusions .= ' AND t.term_id <> ' . intval($exterm) . ' ';
			}
		}
	}

	if ( !empty($exclude) ) {
		$exterms = wp_parse_id_list($exclude);
		foreach ( $exterms as $exterm ) {
			if ( empty($exclusions) )
				$exclusions = ' AND ( t.term_id <> ' . intval($exterm) . ' ';
			else
				$exclusions .= ' AND t.term_id <> ' . intval($exterm) . ' ';
		}
	}

	if ( !empty($exclusions) )
		$exclusions .= ')';
	$exclusions = apply_filters('list_terms_exclusions', $exclusions, $args );
	$where .= $exclusions;

	if ( !empty($slug) ) {
		$slug = sanitize_title($slug);
		$where .= " AND t.slug = '$slug'";
	}

	if ( !empty($name__like) )
		$where .= " AND t.name LIKE '{$name__like}%'";

	if ( '' !== $parent ) {
		$parent = (int) $parent;
		$where .= " AND tt.parent = '$parent'";
	}

	if ( $hide_empty && !$hierarchical )
		$where .= ' AND tt.count > 0';

	// don't limit the query results when we have to descend the family tree
	if ( ! empty($number) && ! $hierarchical && empty( $child_of ) && '' === $parent ) {
		if ( $offset )
			$limits = 'LIMIT ' . $offset . ',' . $number;
		else
			$limits = 'LIMIT ' . $number;
	} else {
		$limits = '';
	}

	if ( !empty($search) ) {
		$search = like_escape($search);
		$where .= " AND (t.name LIKE '%$search%')";
	}

	$selects = array();
	switch ( $fields ) {
		case 'all':
			$selects = array('t.*', 'tt.*');
			break;
		case 'ids':
		case 'id=>parent':
			$selects = array('t.term_id', 'tt.parent', 'tt.count');
			break;
		case 'names':
			$selects = array('t.term_id', 'tt.parent', 'tt.count', 't.name');
			break;
		case 'count':
			$orderby = '';
			$order = '';
			$selects = array('COUNT(*)');
	}

	$_fields = $fields;

	$fields = implode(', ', apply_filters( 'get_terms_fields', $selects, $args ));

	$join = "INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id";

	$pieces = array( 'fields', 'join', 'where', 'orderby', 'order', 'limits' );
	$clauses = apply_filters( 'terms_clauses', compact( $pieces ), $taxonomies, $args );
	foreach ( $pieces as $piece )
		$$piece = isset( $clauses[ $piece ] ) ? $clauses[ $piece ] : '';

	$query = "SELECT $fields FROM $wpdb->terms AS t $join WHERE $where $orderby $order $limits";

	$fields = $_fields;

	if ( 'count' == $fields ) {
		$term_count = $wpdb->get_var($query);
		return $term_count;
	}

	$terms = $wpdb->get_results($query);
	if ( 'all' == $fields ) {
		update_term_cache($terms);
	}

	if ( empty($terms) ) {
		wp_cache_add( $cache_key, array(), 'terms', 86400 ); // one day
		$terms = apply_filters('get_terms', array(), $taxonomies, $args);
		return $terms;
	}

	if ( $child_of ) {
		$children = _get_term_hierarchy($taxonomies[0]);
		if ( ! empty($children) )
			$terms = & _get_term_children($child_of, $terms, $taxonomies[0]);
	}

	// Update term counts to include children.
	if ( $pad_counts && 'all' == $fields )
		_pad_term_counts($terms, $taxonomies[0]);

	// Make sure we show empty categories that have children.
	if ( $hierarchical && $hide_empty && is_array($terms) ) {
		foreach ( $terms as $k => $term ) {
			if ( ! $term->count ) {
				$children = _get_term_children($term->term_id, $terms, $taxonomies[0]);
				if ( is_array($children) )
					foreach ( $children as $child )
						if ( $child->count )
							continue 2;

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

	$_terms = array();
	if ( 'id=>parent' == $fields ) {
		while ( $term = array_shift($terms) )
			$_terms[$term->term_id] = $term->parent;
		$terms = $_terms;
	} elseif ( 'ids' == $fields ) {
		while ( $term = array_shift($terms) )
			$_terms[] = $term->term_id;
		$terms = $_terms;
	} elseif ( 'names' == $fields ) {
		while ( $term = array_shift($terms) )
			$_terms[] = $term->name;
		$terms = $_terms;
	}

	if ( 0 < $number && intval(@count($terms)) > $number ) {
		$terms = array_slice($terms, $offset, $number);
	}

	wp_cache_add( $cache_key, $terms, 'terms', 86400 ); // one day

	$terms = apply_filters('get_terms', $terms, $taxonomies, $args);
	return $terms;
}

/**
 * Check if Term exists.
 *
 * Returns the index of a defined term, or 0 (false) if the term doesn't exist.
 *
 * Formerly is_term(), introduced in 2.3.0.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 3.0.0
 *
 * @uses $wpdb
 *
 * @param int|string $term The term to check
 * @param string $taxonomy The taxonomy name to use
 * @param int $parent ID of parent term under which to confine the exists search.
 * @return mixed Get the term id or Term Object, if exists.
 */
function term_exists($term, $taxonomy = '', $parent = 0) {
	global $wpdb;

	$select = "SELECT term_id FROM $wpdb->terms as t WHERE ";
	$tax_select = "SELECT tt.term_id, tt.term_taxonomy_id FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy as tt ON tt.term_id = t.term_id WHERE ";

	if ( is_int($term) ) {
		if ( 0 == $term )
			return 0;
		$where = 't.term_id = %d';
		if ( !empty($taxonomy) )
			return $wpdb->get_row( $wpdb->prepare( $tax_select . $where . " AND tt.taxonomy = %s", $term, $taxonomy ), ARRAY_A );
		else
			return $wpdb->get_var( $wpdb->prepare( $select . $where, $term ) );
	}

	$term = trim( stripslashes( $term ) );

	if ( '' === $slug = sanitize_title($term) )
		return 0;

	$where = 't.slug = %s';
	$else_where = 't.name = %s';
	$where_fields = array($slug);
	$else_where_fields = array($term);
	if ( !empty($taxonomy) ) {
		$parent = (int) $parent;
		if ( $parent > 0 ) {
			$where_fields[] = $parent;
			$else_where_fields[] = $parent;
			$where .= ' AND tt.parent = %d';
			$else_where .= ' AND tt.parent = %d';
		}

		$where_fields[] = $taxonomy;
		$else_where_fields[] = $taxonomy;

		if ( $result = $wpdb->get_row( $wpdb->prepare("SELECT tt.term_id, tt.term_taxonomy_id FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy as tt ON tt.term_id = t.term_id WHERE $where AND tt.taxonomy = %s", $where_fields), ARRAY_A) )
			return $result;

		return $wpdb->get_row( $wpdb->prepare("SELECT tt.term_id, tt.term_taxonomy_id FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy as tt ON tt.term_id = t.term_id WHERE $else_where AND tt.taxonomy = %s", $else_where_fields), ARRAY_A);
	}

	if ( $result = $wpdb->get_var( $wpdb->prepare("SELECT term_id FROM $wpdb->terms as t WHERE $where", $where_fields) ) )
		return $result;

	return $wpdb->get_var( $wpdb->prepare("SELECT term_id FROM $wpdb->terms as t WHERE $else_where", $else_where_fields) );
}

/**
 * Sanitize Term all fields.
 *
 * Relys on sanitize_term_field() to sanitize the term. The difference is that
 * this function will sanitize <strong>all</strong> fields. The context is based
 * on sanitize_term_field().
 *
 * The $term is expected to be either an array or an object.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses sanitize_term_field Used to sanitize all fields in a term
 *
 * @param array|object $term The term to check
 * @param string $taxonomy The taxonomy name to use
 * @param string $context Default is 'display'.
 * @return array|object Term with all fields sanitized
 */
function sanitize_term($term, $taxonomy, $context = 'display') {

	if ( 'raw' == $context )
		return $term;

	$fields = array('term_id', 'name', 'description', 'slug', 'count', 'parent', 'term_group');

	$do_object = false;
	if ( is_object($term) )
		$do_object = true;

	$term_id = $do_object ? $term->term_id : (isset($term['term_id']) ? $term['term_id'] : 0);

	foreach ( (array) $fields as $field ) {
		if ( $do_object ) {
			if ( isset($term->$field) )
				$term->$field = sanitize_term_field($field, $term->$field, $term_id, $taxonomy, $context);
		} else {
			if ( isset($term[$field]) )
				$term[$field] = sanitize_term_field($field, $term[$field], $term_id, $taxonomy, $context);
		}
	}

	if ( $do_object )
		$term->filter = $context;
	else
		$term['filter'] = $context;

	return $term;
}

/**
 * Cleanse the field value in the term based on the context.
 *
 * Passing a term field value through the function should be assumed to have
 * cleansed the value for whatever context the term field is going to be used.
 *
 * If no context or an unsupported context is given, then default filters will
 * be applied.
 *
 * There are enough filters for each context to support a custom filtering
 * without creating your own filter function. Simply create a function that
 * hooks into the filter you need.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses $wpdb
 *
 * @param string $field Term field to sanitize
 * @param string $value Search for this term value
 * @param int $term_id Term ID
 * @param string $taxonomy Taxonomy Name
 * @param string $context Either edit, db, display, attribute, or js.
 * @return mixed sanitized field
 */
function sanitize_term_field($field, $value, $term_id, $taxonomy, $context) {
	if ( 'parent' == $field  || 'term_id' == $field || 'count' == $field || 'term_group' == $field ) {
		$value = (int) $value;
		if ( $value < 0 )
			$value = 0;
	}

	if ( 'raw' == $context )
		return $value;

	if ( 'edit' == $context ) {
		$value = apply_filters("edit_term_{$field}", $value, $term_id, $taxonomy);
		$value = apply_filters("edit_{$taxonomy}_{$field}", $value, $term_id);
		if ( 'description' == $field )
			$value = format_to_edit($value);
		else
			$value = esc_attr($value);
	} else if ( 'db' == $context ) {
		$value = apply_filters("pre_term_{$field}", $value, $taxonomy);
		$value = apply_filters("pre_{$taxonomy}_{$field}", $value);
		// Back compat filters
		if ( 'slug' == $field )
			$value = apply_filters('pre_category_nicename', $value);

	} else if ( 'rss' == $context ) {
		$value = apply_filters("term_{$field}_rss", $value, $taxonomy);
		$value = apply_filters("{$taxonomy}_{$field}_rss", $value);
	} else {
		// Use display filters by default.
		$value = apply_filters("term_{$field}", $value, $term_id, $taxonomy, $context);
		$value = apply_filters("{$taxonomy}_{$field}", $value, $term_id, $context);
	}

	if ( 'attribute' == $context )
		$value = esc_attr($value);
	else if ( 'js' == $context )
		$value = esc_js($value);

	return $value;
}

/**
 * Count how many terms are in Taxonomy.
 *
 * Default $args is 'hide_empty' which can be 'hide_empty=true' or array('hide_empty' => true).
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses get_terms()
 * @uses wp_parse_args() Turns strings into arrays and merges defaults into an array.
 *
 * @param string $taxonomy Taxonomy name
 * @param array|string $args Overwrite defaults. See get_terms()
 * @return int How many terms are in $taxonomy
 */
function wp_count_terms( $taxonomy, $args = array() ) {
	$defaults = array('hide_empty' => false);
	$args = wp_parse_args($args, $defaults);

	// backwards compatibility
	if ( isset($args['ignore_empty']) ) {
		$args['hide_empty'] = $args['ignore_empty'];
		unset($args['ignore_empty']);
	}

	$args['fields'] = 'count';

	return get_terms($taxonomy, $args);
}

/**
 * Will unlink the object from the taxonomy or taxonomies.
 *
 * Will remove all relationships between the object and any terms in 
 * a particular taxonomy or taxonomies. Does not remove the term or 
 * taxonomy itself.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 * @uses $wpdb
 *
 * @param int $object_id The term Object Id that refers to the term
 * @param string|array $taxonomies List of Taxonomy Names or single Taxonomy name.
 */
function wp_delete_object_term_relationships( $object_id, $taxonomies ) {
	global $wpdb;

	$object_id = (int) $object_id;

	if ( !is_array($taxonomies) )
		$taxonomies = array($taxonomies);

	foreach ( (array) $taxonomies as $taxonomy ) {
		$tt_ids = wp_get_object_terms($object_id, $taxonomy, array('fields' => 'tt_ids'));
		$in_tt_ids = "'" . implode("', '", $tt_ids) . "'";
		do_action( 'delete_term_relationships', $object_id, $tt_ids );
		$wpdb->query( $wpdb->prepare("DELETE FROM $wpdb->term_relationships WHERE object_id = %d AND term_taxonomy_id IN ($in_tt_ids)", $object_id) );
		do_action( 'deleted_term_relationships', $object_id, $tt_ids );
		wp_update_term_count($tt_ids, $taxonomy);
	}
}

/**
 * Removes a term from the database.
 *
 * If the term is a parent of other terms, then the children will be updated to
 * that term's parent.
 *
 * The $args 'default' will only override the terms found, if there is only one
 * term found. Any other and the found terms are used.
 *
 * The $args 'force_default' will force the term supplied as default to be
 * assigned even if the object was not going to be termless
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses $wpdb
 * @uses do_action() Calls both 'delete_term' and 'delete_$taxonomy' action
 *	hooks, passing term object, term id. 'delete_term' gets an additional
 *	parameter with the $taxonomy parameter.
 *
 * @param int $term Term ID
 * @param string $taxonomy Taxonomy Name
 * @param array|string $args Optional. Change 'default' term id and override found term ids.
 * @return bool|WP_Error Returns false if not term; true if completes delete action.
 */
function wp_delete_term( $term, $taxonomy, $args = array() ) {
	global $wpdb;

	$term = (int) $term;

	if ( ! $ids = term_exists($term, $taxonomy) )
		return false;
	if ( is_wp_error( $ids ) )
		return $ids;

	$tt_id = $ids['term_taxonomy_id'];

	$defaults = array();

	if ( 'category' == $taxonomy ) {
		$defaults['default'] = get_option( 'default_category' );
		if ( $defaults['default'] == $term )
			return 0; // Don't delete the default category
	}

	$args = wp_parse_args($args, $defaults);
	extract($args, EXTR_SKIP);

	if ( isset( $default ) ) {
		$default = (int) $default;
		if ( ! term_exists($default, $taxonomy) )
			unset($default);
	}

	// Update children to point to new parent
	if ( is_taxonomy_hierarchical($taxonomy) ) {
		$term_obj = get_term($term, $taxonomy);
		if ( is_wp_error( $term_obj ) )
			return $term_obj;
		$parent = $term_obj->parent;

		$edit_tt_ids = $wpdb->get_col( "SELECT `term_taxonomy_id` FROM $wpdb->term_taxonomy WHERE `parent` = " . (int)$term_obj->term_id );
		do_action( 'edit_term_taxonomies', $edit_tt_ids );
		$wpdb->update( $wpdb->term_taxonomy, compact( 'parent' ), array( 'parent' => $term_obj->term_id) + compact( 'taxonomy' ) );
		do_action( 'edited_term_taxonomies', $edit_tt_ids );
	}

	$objects = $wpdb->get_col( $wpdb->prepare( "SELECT object_id FROM $wpdb->term_relationships WHERE term_taxonomy_id = %d", $tt_id ) );

	foreach ( (array) $objects as $object ) {
		$terms = wp_get_object_terms($object, $taxonomy, array('fields' => 'ids', 'orderby' => 'none'));
		if ( 1 == count($terms) && isset($default) ) {
			$terms = array($default);
		} else {
			$terms = array_diff($terms, array($term));
			if (isset($default) && isset($force_default) && $force_default)
				$terms = array_merge($terms, array($default));
		}
		$terms = array_map('intval', $terms);
		wp_set_object_terms($object, $terms, $taxonomy);
	}

	do_action( 'delete_term_taxonomy', $tt_id );
	$wpdb->query( $wpdb->prepare( "DELETE FROM $wpdb->term_taxonomy WHERE term_taxonomy_id = %d", $tt_id ) );
	do_action( 'deleted_term_taxonomy', $tt_id );

	// Delete the term if no taxonomies use it.
	if ( !$wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM $wpdb->term_taxonomy WHERE term_id = %d", $term) ) )
		$wpdb->query( $wpdb->prepare( "DELETE FROM $wpdb->terms WHERE term_id = %d", $term) );

	clean_term_cache($term, $taxonomy);

	do_action('delete_term', $term, $tt_id, $taxonomy);
	do_action("delete_$taxonomy", $term, $tt_id);

	return true;
}

/*
 * Deletes one existing category.
 *
 * @since 2.0.0
 * @uses wp_delete_term()
 *
 * @param int $cat_ID
 * @return mixed Returns true if completes delete action; false if term doesnt exist;
 * 	Zero on attempted deletion of default Category; WP_Error object is also a possibility.
 */
function wp_delete_category( $cat_ID ) {
	return wp_delete_term( $cat_ID, 'category' );
}

/**
 * Retrieves the terms associated with the given object(s), in the supplied taxonomies.
 *
 * The following information has to do the $args parameter and for what can be
 * contained in the string or array of that parameter, if it exists.
 *
 * The first argument is called, 'orderby' and has the default value of 'name'.
 * The other value that is supported is 'count'.
 *
 * The second argument is called, 'order' and has the default value of 'ASC'.
 * The only other value that will be acceptable is 'DESC'.
 *
 * The final argument supported is called, 'fields' and has the default value of
 * 'all'. There are multiple other options that can be used instead. Supported
 * values are as follows: 'all', 'ids', 'names', and finally
 * 'all_with_object_id'.
 *
 * The fields argument also decides what will be returned. If 'all' or
 * 'all_with_object_id' is choosen or the default kept intact, then all matching
 * terms objects will be returned. If either 'ids' or 'names' is used, then an
 * array of all matching term ids or term names will be returned respectively.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 * @uses $wpdb
 *
 * @param int|array $object_ids The ID(s) of the object(s) to retrieve.
 * @param string|array $taxonomies The taxonomies to retrieve terms from.
 * @param array|string $args Change what is returned
 * @return array|WP_Error The requested term data or empty array if no terms found. WP_Error if $taxonomy does not exist.
 */
function wp_get_object_terms($object_ids, $taxonomies, $args = array()) {
	global $wpdb;

	if ( !is_array($taxonomies) )
		$taxonomies = array($taxonomies);

	foreach ( (array) $taxonomies as $taxonomy ) {
		if ( ! taxonomy_exists($taxonomy) )
			return new WP_Error('invalid_taxonomy', __('Invalid Taxonomy'));
	}

	if ( !is_array($object_ids) )
		$object_ids = array($object_ids);
	$object_ids = array_map('intval', $object_ids);

	$defaults = array('orderby' => 'name', 'order' => 'ASC', 'fields' => 'all');
	$args = wp_parse_args( $args, $defaults );

	$terms = array();
	if ( count($taxonomies) > 1 ) {
		foreach ( $taxonomies as $index => $taxonomy ) {
			$t = get_taxonomy($taxonomy);
			if ( isset($t->args) && is_array($t->args) && $args != array_merge($args, $t->args) ) {
				unset($taxonomies[$index]);
				$terms = array_merge($terms, wp_get_object_terms($object_ids, $taxonomy, array_merge($args, $t->args)));
			}
		}
	} else {
		$t = get_taxonomy($taxonomies[0]);
		if ( isset($t->args) && is_array($t->args) )
			$args = array_merge($args, $t->args);
	}

	extract($args, EXTR_SKIP);

	if ( 'count' == $orderby )
		$orderby = 'tt.count';
	else if ( 'name' == $orderby )
		$orderby = 't.name';
	else if ( 'slug' == $orderby )
		$orderby = 't.slug';
	else if ( 'term_group' == $orderby )
		$orderby = 't.term_group';
	else if ( 'term_order' == $orderby )
		$orderby = 'tr.term_order';
	else if ( 'none' == $orderby ) {
		$orderby = '';
		$order = '';
	} else {
		$orderby = 't.term_id';
	}

	// tt_ids queries can only be none or tr.term_taxonomy_id
	if ( ('tt_ids' == $fields) && !empty($orderby) )
		$orderby = 'tr.term_taxonomy_id';

	if ( !empty($orderby) )
		$orderby = "ORDER BY $orderby";

	$taxonomies = "'" . implode("', '", $taxonomies) . "'";
	$object_ids = implode(', ', $object_ids);

	$select_this = '';
	if ( 'all' == $fields )
		$select_this = 't.*, tt.*';
	else if ( 'ids' == $fields )
		$select_this = 't.term_id';
	else if ( 'names' == $fields )
		$select_this = 't.name';
	else if ( 'all_with_object_id' == $fields )
		$select_this = 't.*, tt.*, tr.object_id';

	$query = "SELECT $select_this FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy AS tt ON tt.term_id = t.term_id INNER JOIN $wpdb->term_relationships AS tr ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tt.taxonomy IN ($taxonomies) AND tr.object_id IN ($object_ids) $orderby $order";

	if ( 'all' == $fields || 'all_with_object_id' == $fields ) {
		$terms = array_merge($terms, $wpdb->get_results($query));
		update_term_cache($terms);
	} else if ( 'ids' == $fields || 'names' == $fields ) {
		$terms = array_merge($terms, $wpdb->get_col($query));
	} else if ( 'tt_ids' == $fields ) {
		$terms = $wpdb->get_col("SELECT tr.term_taxonomy_id FROM $wpdb->term_relationships AS tr INNER JOIN $wpdb->term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tr.object_id IN ($object_ids) AND tt.taxonomy IN ($taxonomies) $orderby $order");
	}

	if ( ! $terms )
		$terms = array();

	return apply_filters('wp_get_object_terms', $terms, $object_ids, $taxonomies, $args);
}

/**
 * Adds a new term to the database. Optionally marks it as an alias of an existing term.
 *
 * Error handling is assigned for the nonexistance of the $taxonomy and $term
 * parameters before inserting. If both the term id and taxonomy exist
 * previously, then an array will be returned that contains the term id and the
 * contents of what is returned. The keys of the array are 'term_id' and
 * 'term_taxonomy_id' containing numeric values.
 *
 * It is assumed that the term does not yet exist or the above will apply. The
 * term will be first added to the term table and then related to the taxonomy
 * if everything is well. If everything is correct, then several actions will be
 * run prior to a filter and then several actions will be run after the filter
 * is run.
 *
 * The arguments decide how the term is handled based on the $args parameter.
 * The following is a list of the available overrides and the defaults.
 *
 * 'alias_of'. There is no default, but if added, expected is the slug that the
 * term will be an alias of. Expected to be a string.
 *
 * 'description'. There is no default. If exists, will be added to the database
 * along with the term. Expected to be a string.
 *
 * 'parent'. Expected to be numeric and default is 0 (zero). Will assign value
 * of 'parent' to the term.
 *
 * 'slug'. Expected to be a string. There is no default.
 *
 * If 'slug' argument exists then the slug will be checked to see if it is not
 * a valid term. If that check succeeds (it is not a valid term), then it is
 * added and the term id is given. If it fails, then a check is made to whether
 * the taxonomy is hierarchical and the parent argument is not empty. If the
 * second check succeeds, the term will be inserted and the term id will be
 * given.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 * @uses $wpdb
 *
 * @uses apply_filters() Calls 'pre_insert_term' hook with term and taxonomy as parameters.
 * @uses do_action() Calls 'create_term' hook with the term id and taxonomy id as parameters.
 * @uses do_action() Calls 'create_$taxonomy' hook with term id and taxonomy id as parameters.
 * @uses apply_filters() Calls 'term_id_filter' hook with term id and taxonomy id as parameters.
 * @uses do_action() Calls 'created_term' hook with the term id and taxonomy id as parameters.
 * @uses do_action() Calls 'created_$taxonomy' hook with term id and taxonomy id as parameters.
 *
 * @param string $term The term to add or update.
 * @param string $taxonomy The taxonomy to which to add the term
 * @param array|string $args Change the values of the inserted term
 * @return array|WP_Error The Term ID and Term Taxonomy ID
 */
function wp_insert_term( $term, $taxonomy, $args = array() ) {
	global $wpdb;

	if ( ! taxonomy_exists($taxonomy) )
		return new WP_Error('invalid_taxonomy', __('Invalid taxonomy'));

	$term = apply_filters( 'pre_insert_term', $term, $taxonomy );
		if ( is_wp_error( $term ) )
			return $term;

	if ( is_int($term) && 0 == $term )
		return new WP_Error('invalid_term_id', __('Invalid term ID'));

	if ( '' == trim($term) )
		return new WP_Error('empty_term_name', __('A name is required for this term'));

	$defaults = array( 'alias_of' => '', 'description' => '', 'parent' => 0, 'slug' => '');
	$args = wp_parse_args($args, $defaults);
	$args['name'] = $term;
	$args['taxonomy'] = $taxonomy;
	$args = sanitize_term($args, $taxonomy, 'db');
	extract($args, EXTR_SKIP);

	// expected_slashed ($name)
	$name = stripslashes($name);
	$description = stripslashes($description);

	if ( empty($slug) )
		$slug = sanitize_title($name);

	$term_group = 0;
	if ( $alias_of ) {
		$alias = $wpdb->get_row( $wpdb->prepare( "SELECT term_id, term_group FROM $wpdb->terms WHERE slug = %s", $alias_of) );
		if ( $alias->term_group ) {
			// The alias we want is already in a group, so let's use that one.
			$term_group = $alias->term_group;
		} else {
			// The alias isn't in a group, so let's create a new one and firstly add the alias term to it.
			$term_group = $wpdb->get_var("SELECT MAX(term_group) FROM $wpdb->terms") + 1;
			do_action( 'edit_terms', $alias->term_id );
			$wpdb->update($wpdb->terms, compact('term_group'), array('term_id' => $alias->term_id) );
			do_action( 'edited_terms', $alias->term_id );
		}
	}

	if ( $term_id = term_exists($slug) ) {
		$existing_term = $wpdb->get_row( $wpdb->prepare( "SELECT name FROM $wpdb->terms WHERE term_id = %d", $term_id), ARRAY_A );
		// We've got an existing term in the same taxonomy, which matches the name of the new term:
		if ( is_taxonomy_hierarchical($taxonomy) && $existing_term['name'] == $name && $exists = term_exists( (int) $term_id, $taxonomy ) ) {
			// Hierarchical, and it matches an existing term, Do not allow same "name" in the same level.
			$siblings = get_terms($taxonomy, array('fields' => 'names', 'get' => 'all', 'parent' => (int)$parent) );
			if ( in_array($name, $siblings) ) {
				return new WP_Error('term_exists', __('A term with the name provided already exists with this parent.'), $exists['term_id']);
			} else {
				$slug = wp_unique_term_slug($slug, (object) $args);
				if ( false === $wpdb->insert( $wpdb->terms, compact( 'name', 'slug', 'term_group' ) ) )
					return new WP_Error('db_insert_error', __('Could not insert term into the database'), $wpdb->last_error);
				$term_id = (int) $wpdb->insert_id;
			}
		} elseif ( $existing_term['name'] != $name ) {
			// We've got an existing term, with a different name, Create the new term.
			$slug = wp_unique_term_slug($slug, (object) $args);
			if ( false === $wpdb->insert( $wpdb->terms, compact( 'name', 'slug', 'term_group' ) ) )
				return new WP_Error('db_insert_error', __('Could not insert term into the database'), $wpdb->last_error);
			$term_id = (int) $wpdb->insert_id;
		} elseif ( $exists = term_exists( (int) $term_id, $taxonomy ) )  {
			// Same name, same slug.
			return new WP_Error('term_exists', __('A term with the name provided already exists.'), $exists['term_id']);
		}
	} else {
		// This term does not exist at all in the database, Create it.
		$slug = wp_unique_term_slug($slug, (object) $args);
		if ( false === $wpdb->insert( $wpdb->terms, compact( 'name', 'slug', 'term_group' ) ) )
			return new WP_Error('db_insert_error', __('Could not insert term into the database'), $wpdb->last_error);
		$term_id = (int) $wpdb->insert_id;
	}

	// Seems unreachable, However, Is used in the case that a term name is provided, which sanitizes to an empty string.
	if ( empty($slug) ) {
		$slug = sanitize_title($slug, $term_id);
		do_action( 'edit_terms', $term_id );
		$wpdb->update( $wpdb->terms, compact( 'slug' ), compact( 'term_id' ) );
		do_action( 'edited_terms', $term_id );
	}

	$tt_id = $wpdb->get_var( $wpdb->prepare( "SELECT tt.term_taxonomy_id FROM $wpdb->term_taxonomy AS tt INNER JOIN $wpdb->terms AS t ON tt.term_id = t.term_id WHERE tt.taxonomy = %s AND t.term_id = %d", $taxonomy, $term_id ) );

	if ( !empty($tt_id) )
		return array('term_id' => $term_id, 'term_taxonomy_id' => $tt_id);

	$wpdb->insert( $wpdb->term_taxonomy, compact( 'term_id', 'taxonomy', 'description', 'parent') + array( 'count' => 0 ) );
	$tt_id = (int) $wpdb->insert_id;

	do_action("create_term", $term_id, $tt_id, $taxonomy);
	do_action("create_$taxonomy", $term_id, $tt_id);

	$term_id = apply_filters('term_id_filter', $term_id, $tt_id);

	clean_term_cache($term_id, $taxonomy);

	do_action("created_term", $term_id, $tt_id, $taxonomy);
	do_action("created_$taxonomy", $term_id, $tt_id);

	return array('term_id' => $term_id, 'term_taxonomy_id' => $tt_id);
}

/**
 * Create Term and Taxonomy Relationships.
 *
 * Relates an object (post, link etc) to a term and taxonomy type. Creates the
 * term and taxonomy relationship if it doesn't already exist. Creates a term if
 * it doesn't exist (using the slug).
 *
 * A relationship means that the term is grouped in or belongs to the taxonomy.
 * A term has no meaning until it is given context by defining which taxonomy it
 * exists under.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 * @uses $wpdb
 *
 * @param int $object_id The object to relate to.
 * @param array|int|string $terms The slug or id of the term, will replace all existing
 * related terms in this taxonomy.
 * @param array|string $taxonomy The context in which to relate the term to the object.
 * @param bool $append If false will delete difference of terms.
 * @return array|WP_Error Affected Term IDs
 */
function wp_set_object_terms($object_id, $terms, $taxonomy, $append = false) {
	global $wpdb;

	$object_id = (int) $object_id;

	if ( ! taxonomy_exists($taxonomy) )
		return new WP_Error('invalid_taxonomy', __('Invalid Taxonomy'));

	if ( !is_array($terms) )
		$terms = array($terms);

	if ( ! $append )
		$old_tt_ids =  wp_get_object_terms($object_id, $taxonomy, array('fields' => 'tt_ids', 'orderby' => 'none'));
	else
		$old_tt_ids = array();

	$tt_ids = array();
	$term_ids = array();

	foreach ( (array) $terms as $term) {
		if ( !strlen(trim($term)) )
			continue;

		if ( !$term_info = term_exists($term, $taxonomy) ) {
			// Skip if a non-existent term ID is passed.
			if ( is_int($term) )
				continue;
			$term_info = wp_insert_term($term, $taxonomy);
		}
		if ( is_wp_error($term_info) )
			return $term_info;
		$term_ids[] = $term_info['term_id'];
		$tt_id = $term_info['term_taxonomy_id'];
		$tt_ids[] = $tt_id;

		if ( $wpdb->get_var( $wpdb->prepare( "SELECT term_taxonomy_id FROM $wpdb->term_relationships WHERE object_id = %d AND term_taxonomy_id = %d", $object_id, $tt_id ) ) )
			continue;
		do_action( 'add_term_relationship', $object_id, $tt_id );
		$wpdb->insert( $wpdb->term_relationships, array( 'object_id' => $object_id, 'term_taxonomy_id' => $tt_id ) );
		do_action( 'added_term_relationship', $object_id, $tt_id );
	}

	wp_update_term_count($tt_ids, $taxonomy);

	if ( ! $append ) {
		$delete_terms = array_diff($old_tt_ids, $tt_ids);
		if ( $delete_terms ) {
			$in_delete_terms = "'" . implode("', '", $delete_terms) . "'";
			do_action( 'delete_term_relationships', $object_id, $delete_terms );
			$wpdb->query( $wpdb->prepare("DELETE FROM $wpdb->term_relationships WHERE object_id = %d AND term_taxonomy_id IN ($in_delete_terms)", $object_id) );
			do_action( 'deleted_term_relationships', $object_id, $delete_terms );
			wp_update_term_count($delete_terms, $taxonomy);
		}
	}

	$t = get_taxonomy($taxonomy);
	if ( ! $append && isset($t->sort) && $t->sort ) {
		$values = array();
		$term_order = 0;
		$final_tt_ids = wp_get_object_terms($object_id, $taxonomy, array('fields' => 'tt_ids'));
		foreach ( $tt_ids as $tt_id )
			if ( in_array($tt_id, $final_tt_ids) )
				$values[] = $wpdb->prepare( "(%d, %d, %d)", $object_id, $tt_id, ++$term_order);
		if ( $values )
			$wpdb->query("INSERT INTO $wpdb->term_relationships (object_id, term_taxonomy_id, term_order) VALUES " . join(',', $values) . " ON DUPLICATE KEY UPDATE term_order = VALUES(term_order)");
	}

	do_action('set_object_terms', $object_id, $terms, $tt_ids, $taxonomy, $append, $old_tt_ids);
	return $tt_ids;
}

/**
 * Will make slug unique, if it isn't already.
 *
 * The $slug has to be unique global to every taxonomy, meaning that one
 * taxonomy term can't have a matching slug with another taxonomy term. Each
 * slug has to be globally unique for every taxonomy.
 *
 * The way this works is that if the taxonomy that the term belongs to is
 * hierarchical and has a parent, it will append that parent to the $slug.
 *
 * If that still doesn't return an unique slug, then it try to append a number
 * until it finds a number that is truely unique.
 *
 * The only purpose for $term is for appending a parent, if one exists.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 * @uses $wpdb
 *
 * @param string $slug The string that will be tried for a unique slug
 * @param object $term The term object that the $slug will belong too
 * @return string Will return a true unique slug.
 */
function wp_unique_term_slug($slug, $term) {
	global $wpdb;

	if ( ! term_exists( $slug ) )
		return $slug;

	// If the taxonomy supports hierarchy and the term has a parent, make the slug unique
	// by incorporating parent slugs.
	if ( is_taxonomy_hierarchical($term->taxonomy) && !empty($term->parent) ) {
		$the_parent = $term->parent;
		while ( ! empty($the_parent) ) {
			$parent_term = get_term($the_parent, $term->taxonomy);
			if ( is_wp_error($parent_term) || empty($parent_term) )
				break;
			$slug .= '-' . $parent_term->slug;
			if ( ! term_exists( $slug ) )
				return $slug;

			if ( empty($parent_term->parent) )
				break;
			$the_parent = $parent_term->parent;
		}
	}

	// If we didn't get a unique slug, try appending a number to make it unique.
	if ( !empty($args['term_id']) )
		$query = $wpdb->prepare( "SELECT slug FROM $wpdb->terms WHERE slug = %s AND term_id != %d", $slug, $args['term_id'] );
	else
		$query = $wpdb->prepare( "SELECT slug FROM $wpdb->terms WHERE slug = %s", $slug );

	if ( $wpdb->get_var( $query ) ) {
		$num = 2;
		do {
			$alt_slug = $slug . "-$num";
			$num++;
			$slug_check = $wpdb->get_var( $wpdb->prepare( "SELECT slug FROM $wpdb->terms WHERE slug = %s", $alt_slug ) );
		} while ( $slug_check );
		$slug = $alt_slug;
	}

	return $slug;
}

/**
 * Update term based on arguments provided.
 *
 * The $args will indiscriminately override all values with the same field name.
 * Care must be taken to not override important information need to update or
 * update will fail (or perhaps create a new term, neither would be acceptable).
 *
 * Defaults will set 'alias_of', 'description', 'parent', and 'slug' if not
 * defined in $args already.
 *
 * 'alias_of' will create a term group, if it doesn't already exist, and update
 * it for the $term.
 *
 * If the 'slug' argument in $args is missing, then the 'name' in $args will be
 * used. It should also be noted that if you set 'slug' and it isn't unique then
 * a WP_Error will be passed back. If you don't pass any slug, then a unique one
 * will be created for you.
 *
 * For what can be overrode in $args, check the term scheme can contain and stay
 * away from the term keys.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses $wpdb
 * @uses do_action() Will call both 'edit_term' and 'edit_$taxonomy' twice.
 * @uses apply_filters() Will call the 'term_id_filter' filter and pass the term
 *	id and taxonomy id.
 *
 * @param int $term_id The ID of the term
 * @param string $taxonomy The context in which to relate the term to the object.
 * @param array|string $args Overwrite term field values
 * @return array|WP_Error Returns Term ID and Taxonomy Term ID
 */
function wp_update_term( $term_id, $taxonomy, $args = array() ) {
	global $wpdb;

	if ( ! taxonomy_exists($taxonomy) )
		return new WP_Error('invalid_taxonomy', __('Invalid taxonomy'));

	$term_id = (int) $term_id;

	// First, get all of the original args
	$term = get_term ($term_id, $taxonomy, ARRAY_A);

	if ( is_wp_error( $term ) )
		return $term;

	// Escape data pulled from DB.
	$term = add_magic_quotes($term);

	// Merge old and new args with new args overwriting old ones.
	$args = array_merge($term, $args);

	$defaults = array( 'alias_of' => '', 'description' => '', 'parent' => 0, 'slug' => '');
	$args = wp_parse_args($args, $defaults);
	$args = sanitize_term($args, $taxonomy, 'db');
	extract($args, EXTR_SKIP);

	// expected_slashed ($name)
	$name = stripslashes($name);
	$description = stripslashes($description);

	if ( '' == trim($name) )
		return new WP_Error('empty_term_name', __('A name is required for this term'));

	$empty_slug = false;
	if ( empty($slug) ) {
		$empty_slug = true;
		$slug = sanitize_title($name);
	}

	if ( $alias_of ) {
		$alias = $wpdb->get_row( $wpdb->prepare( "SELECT term_id, term_group FROM $wpdb->terms WHERE slug = %s", $alias_of) );
		if ( $alias->term_group ) {
			// The alias we want is already in a group, so let's use that one.
			$term_group = $alias->term_group;
		} else {
			// The alias isn't in a group, so let's create a new one and firstly add the alias term to it.
			$term_group = $wpdb->get_var("SELECT MAX(term_group) FROM $wpdb->terms") + 1;
			do_action( 'edit_terms', $alias->term_id );
			$wpdb->update( $wpdb->terms, compact('term_group'), array( 'term_id' => $alias->term_id ) );
			do_action( 'edited_terms', $alias->term_id );
		}
	}

	// Check $parent to see if it will cause a hierarchy loop
	$parent = apply_filters( 'wp_update_term_parent', $parent, $term_id, $taxonomy, compact( array_keys( $args ) ), $args );

	// Check for duplicate slug
	$id = $wpdb->get_var( $wpdb->prepare( "SELECT term_id FROM $wpdb->terms WHERE slug = %s", $slug ) );
	if ( $id && ($id != $term_id) ) {
		// If an empty slug was passed or the parent changed, reset the slug to something unique.
		// Otherwise, bail.
		if ( $empty_slug || ( $parent != $term['parent']) )
			$slug = wp_unique_term_slug($slug, (object) $args);
		else
			return new WP_Error('duplicate_term_slug', sprintf(__('The slug &#8220;%s&#8221; is already in use by another term'), $slug));
	}
	do_action( 'edit_terms', $term_id );
	$wpdb->update($wpdb->terms, compact( 'name', 'slug', 'term_group' ), compact( 'term_id' ) );
	if ( empty($slug) ) {
		$slug = sanitize_title($name, $term_id);
		$wpdb->update( $wpdb->terms, compact( 'slug' ), compact( 'term_id' ) );
	}
	do_action( 'edited_terms', $term_id );

	$tt_id = $wpdb->get_var( $wpdb->prepare( "SELECT tt.term_taxonomy_id FROM $wpdb->term_taxonomy AS tt INNER JOIN $wpdb->terms AS t ON tt.term_id = t.term_id WHERE tt.taxonomy = %s AND t.term_id = %d", $taxonomy, $term_id) );
	do_action( 'edit_term_taxonomy', $tt_id, $taxonomy );
	$wpdb->update( $wpdb->term_taxonomy, compact( 'term_id', 'taxonomy', 'description', 'parent' ), array( 'term_taxonomy_id' => $tt_id ) );
	do_action( 'edited_term_taxonomy', $tt_id, $taxonomy );

	do_action("edit_term", $term_id, $tt_id, $taxonomy);
	do_action("edit_$taxonomy", $term_id, $tt_id);

	$term_id = apply_filters('term_id_filter', $term_id, $tt_id);

	clean_term_cache($term_id, $taxonomy);

	do_action("edited_term", $term_id, $tt_id, $taxonomy);
	do_action("edited_$taxonomy", $term_id, $tt_id);

	return array('term_id' => $term_id, 'term_taxonomy_id' => $tt_id);
}

/**
 * Enable or disable term counting.
 *
 * @since 2.5.0
 *
 * @param bool $defer Optional. Enable if true, disable if false.
 * @return bool Whether term counting is enabled or disabled.
 */
function wp_defer_term_counting($defer=null) {
	static $_defer = false;

	if ( is_bool($defer) ) {
		$_defer = $defer;
		// flush any deferred counts
		if ( !$defer )
			wp_update_term_count( null, null, true );
	}

	return $_defer;
}

/**
 * Updates the amount of terms in taxonomy.
 *
 * If there is a taxonomy callback applyed, then it will be called for updating
 * the count.
 *
 * The default action is to count what the amount of terms have the relationship
 * of term ID. Once that is done, then update the database.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 * @uses $wpdb
 *
 * @param int|array $terms The term_taxonomy_id of the terms
 * @param string $taxonomy The context of the term.
 * @return bool If no terms will return false, and if successful will return true.
 */
function wp_update_term_count( $terms, $taxonomy, $do_deferred=false ) {
	static $_deferred = array();

	if ( $do_deferred ) {
		foreach ( (array) array_keys($_deferred) as $tax ) {
			wp_update_term_count_now( $_deferred[$tax], $tax );
			unset( $_deferred[$tax] );
		}
	}

	if ( empty($terms) )
		return false;

	if ( !is_array($terms) )
		$terms = array($terms);

	if ( wp_defer_term_counting() ) {
		if ( !isset($_deferred[$taxonomy]) )
			$_deferred[$taxonomy] = array();
		$_deferred[$taxonomy] = array_unique( array_merge($_deferred[$taxonomy], $terms) );
		return true;
	}

	return wp_update_term_count_now( $terms, $taxonomy );
}

/**
 * Perform term count update immediately.
 *
 * @since 2.5.0
 *
 * @param array $terms The term_taxonomy_id of terms to update.
 * @param string $taxonomy The context of the term.
 * @return bool Always true when complete.
 */
function wp_update_term_count_now( $terms, $taxonomy ) {
	global $wpdb;

	$terms = array_map('intval', $terms);

	$taxonomy = get_taxonomy($taxonomy);
	if ( !empty($taxonomy->update_count_callback) ) {
		call_user_func($taxonomy->update_count_callback, $terms, $taxonomy);
	} else {
		// Default count updater
		foreach ( (array) $terms as $term) {
			$count = $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM $wpdb->term_relationships WHERE term_taxonomy_id = %d", $term) );
			do_action( 'edit_term_taxonomy', $term, $taxonomy );
			$wpdb->update( $wpdb->term_taxonomy, compact( 'count' ), array( 'term_taxonomy_id' => $term ) );
			do_action( 'edited_term_taxonomy', $term, $taxonomy );
		}

	}

	clean_term_cache($terms, '', false);

	return true;
}

//
// Cache
//


/**
 * Removes the taxonomy relationship to terms from the cache.
 *
 * Will remove the entire taxonomy relationship containing term $object_id. The
 * term IDs have to exist within the taxonomy $object_type for the deletion to
 * take place.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @see get_object_taxonomies() for more on $object_type
 * @uses do_action() Will call action hook named, 'clean_object_term_cache' after completion.
 *	Passes, function params in same order.
 *
 * @param int|array $object_ids Single or list of term object ID(s)
 * @param array|string $object_type The taxonomy object type
 */
function clean_object_term_cache($object_ids, $object_type) {
	if ( !is_array($object_ids) )
		$object_ids = array($object_ids);

	foreach ( $object_ids as $id )
		foreach ( get_object_taxonomies($object_type) as $taxonomy )
			wp_cache_delete($id, "{$taxonomy}_relationships");

	do_action('clean_object_term_cache', $object_ids, $object_type);
}


/**
 * Will remove all of the term ids from the cache.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 * @uses $wpdb
 *
 * @param int|array $ids Single or list of Term IDs
 * @param string $taxonomy Can be empty and will assume tt_ids, else will use for context.
 * @param bool $clean_taxonomy Whether to clean taxonomy wide caches (true), or just individual term object caches (false). Default is true.
 */
function clean_term_cache($ids, $taxonomy = '', $clean_taxonomy = true) {
	global $wpdb;
	static $cleaned = array();

	if ( !is_array($ids) )
		$ids = array($ids);

	$taxonomies = array();
	// If no taxonomy, assume tt_ids.
	if ( empty($taxonomy) ) {
		$tt_ids = array_map('intval', $ids);
		$tt_ids = implode(', ', $tt_ids);
		$terms = $wpdb->get_results("SELECT term_id, taxonomy FROM $wpdb->term_taxonomy WHERE term_taxonomy_id IN ($tt_ids)");
		$ids = array();
		foreach ( (array) $terms as $term ) {
			$taxonomies[] = $term->taxonomy;
			$ids[] = $term->term_id;
			wp_cache_delete($term->term_id, $term->taxonomy);
		}
		$taxonomies = array_unique($taxonomies);
	} else {
		$taxonomies = array($taxonomy);
		foreach ( $taxonomies as $taxonomy ) {
			foreach ( $ids as $id ) {
				wp_cache_delete($id, $taxonomy);
			}
		}
	}

	foreach ( $taxonomies as $taxonomy ) {
		if ( isset($cleaned[$taxonomy]) )
			continue;
		$cleaned[$taxonomy] = true;

		if ( $clean_taxonomy ) {
			wp_cache_delete('all_ids', $taxonomy);
			wp_cache_delete('get', $taxonomy);
			delete_option("{$taxonomy}_children");
			// Regenerate {$taxonomy}_children
			_get_term_hierarchy($taxonomy);
		}

		do_action('clean_term_cache', $ids, $taxonomy);
	}

	wp_cache_set('last_changed', time(), 'terms');
}


/**
 * Retrieves the taxonomy relationship to the term object id.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses wp_cache_get() Retrieves taxonomy relationship from cache
 *
 * @param int|array $id Term object ID
 * @param string $taxonomy Taxonomy Name
 * @return bool|array Empty array if $terms found, but not $taxonomy. False if nothing is in cache for $taxonomy and $id.
 */
function &get_object_term_cache($id, $taxonomy) {
	$cache = wp_cache_get($id, "{$taxonomy}_relationships");
	return $cache;
}


/**
 * Updates the cache for Term ID(s).
 *
 * Will only update the cache for terms not already cached.
 *
 * The $object_ids expects that the ids be separated by commas, if it is a
 * string.
 *
 * It should be noted that update_object_term_cache() is very time extensive. It
 * is advised that the function is not called very often or at least not for a
 * lot of terms that exist in a lot of taxonomies. The amount of time increases
 * for each term and it also increases for each taxonomy the term belongs to.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 * @uses wp_get_object_terms() Used to get terms from the database to update
 *
 * @param string|array $object_ids Single or list of term object ID(s)
 * @param array|string $object_type The taxonomy object type
 * @return null|bool Null value is given with empty $object_ids. False if
 */
function update_object_term_cache($object_ids, $object_type) {
	if ( empty($object_ids) )
		return;

	if ( !is_array($object_ids) )
		$object_ids = explode(',', $object_ids);

	$object_ids = array_map('intval', $object_ids);

	$taxonomies = get_object_taxonomies($object_type);

	$ids = array();
	foreach ( (array) $object_ids as $id ) {
		foreach ( $taxonomies as $taxonomy ) {
			if ( false === wp_cache_get($id, "{$taxonomy}_relationships") ) {
				$ids[] = $id;
				break;
			}
		}
	}

	if ( empty( $ids ) )
		return false;

	$terms = wp_get_object_terms($ids, $taxonomies, array('fields' => 'all_with_object_id'));

	$object_terms = array();
	foreach ( (array) $terms as $term )
		$object_terms[$term->object_id][$term->taxonomy][$term->term_id] = $term;

	foreach ( $ids as $id ) {
		foreach ( $taxonomies  as $taxonomy ) {
			if ( ! isset($object_terms[$id][$taxonomy]) ) {
				if ( !isset($object_terms[$id]) )
					$object_terms[$id] = array();
				$object_terms[$id][$taxonomy] = array();
			}
		}
	}

	foreach ( $object_terms as $id => $value ) {
		foreach ( $value as $taxonomy => $terms ) {
			wp_cache_set($id, $terms, "{$taxonomy}_relationships");
		}
	}
}


/**
 * Updates Terms to Taxonomy in cache.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @since 2.3.0
 *
 * @param array $terms List of Term objects to change
 * @param string $taxonomy Optional. Update Term to this taxonomy in cache
 */
function update_term_cache($terms, $taxonomy = '') {
	foreach ( (array) $terms as $term ) {
		$term_taxonomy = $taxonomy;
		if ( empty($term_taxonomy) )
			$term_taxonomy = $term->taxonomy;

		wp_cache_add($term->term_id, $term, $term_taxonomy);
	}
}

//
// Private
//


/**
 * Retrieves children of taxonomy as Term IDs.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @access private
 * @since 2.3.0
 *
 * @uses update_option() Stores all of the children in "$taxonomy_children"
 *	 option. That is the name of the taxonomy, immediately followed by '_children'.
 *
 * @param string $taxonomy Taxonomy Name
 * @return array Empty if $taxonomy isn't hierarchical or returns children as Term IDs.
 */
function _get_term_hierarchy($taxonomy) {
	if ( !is_taxonomy_hierarchical($taxonomy) )
		return array();
	$children = get_option("{$taxonomy}_children");

	if ( is_array($children) )
		return $children;
	$children = array();
	$terms = get_terms($taxonomy, array('get' => 'all', 'orderby' => 'id', 'fields' => 'id=>parent'));
	foreach ( $terms as $term_id => $parent ) {
		if ( $parent > 0 )
			$children[$parent][] = $term_id;
	}
	update_option("{$taxonomy}_children", $children);

	return $children;
}


/**
 * Get the subset of $terms that are descendants of $term_id.
 *
 * If $terms is an array of objects, then _get_term_children returns an array of objects.
 * If $terms is an array of IDs, then _get_term_children returns an array of IDs.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @access private
 * @since 2.3.0
 *
 * @param int $term_id The ancestor term: all returned terms should be descendants of $term_id.
 * @param array $terms The set of terms---either an array of term objects or term IDs---from which those that are descendants of $term_id will be chosen.
 * @param string $taxonomy The taxonomy which determines the hierarchy of the terms.
 * @return array The subset of $terms that are descendants of $term_id.
 */
function &_get_term_children($term_id, $terms, $taxonomy) {
	$empty_array = array();
	if ( empty($terms) )
		return $empty_array;

	$term_list = array();
	$has_children = _get_term_hierarchy($taxonomy);

	if  ( ( 0 != $term_id ) && ! isset($has_children[$term_id]) )
		return $empty_array;

	foreach ( (array) $terms as $term ) {
		$use_id = false;
		if ( !is_object($term) ) {
			$term = get_term($term, $taxonomy);
			if ( is_wp_error( $term ) )
				return $term;
			$use_id = true;
		}

		if ( $term->term_id == $term_id )
			continue;

		if ( $term->parent == $term_id ) {
			if ( $use_id )
				$term_list[] = $term->term_id;
			else
				$term_list[] = $term;

			if ( !isset($has_children[$term->term_id]) )
				continue;

			if ( $children = _get_term_children($term->term_id, $terms, $taxonomy) )
				$term_list = array_merge($term_list, $children);
		}
	}

	return $term_list;
}


/**
 * Add count of children to parent count.
 *
 * Recalculates term counts by including items from child terms. Assumes all
 * relevant children are already in the $terms argument.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @access private
 * @since 2.3.0
 * @uses $wpdb
 *
 * @param array $terms List of Term IDs
 * @param string $taxonomy Term Context
 * @return null Will break from function if conditions are not met.
 */
function _pad_term_counts(&$terms, $taxonomy) {
	global $wpdb;

	// This function only works for hierarchical taxonomies like post categories.
	if ( !is_taxonomy_hierarchical( $taxonomy ) )
		return;

	$term_hier = _get_term_hierarchy($taxonomy);

	if ( empty($term_hier) )
		return;

	$term_items = array();

	foreach ( (array) $terms as $key => $term ) {
		$terms_by_id[$term->term_id] = & $terms[$key];
		$term_ids[$term->term_taxonomy_id] = $term->term_id;
	}

	// Get the object and term ids and stick them in a lookup table
	$tax_obj = get_taxonomy($taxonomy);
	$object_types = esc_sql($tax_obj->object_type);
	$results = $wpdb->get_results("SELECT object_id, term_taxonomy_id FROM $wpdb->term_relationships INNER JOIN $wpdb->posts ON object_id = ID WHERE term_taxonomy_id IN (" . implode(',', array_keys($term_ids)) . ") AND post_type IN ('" . implode("', '", $object_types) . "') AND post_status = 'publish'");
	foreach ( $results as $row ) {
		$id = $term_ids[$row->term_taxonomy_id];
		$term_items[$id][$row->object_id] = isset($term_items[$id][$row->object_id]) ? ++$term_items[$id][$row->object_id] : 1;
	}

	// Touch every ancestor's lookup row for each post in each term
	foreach ( $term_ids as $term_id ) {
		$child = $term_id;
		while ( $parent = $terms_by_id[$child]->parent ) {
			if ( !empty($term_items[$term_id]) )
				foreach ( $term_items[$term_id] as $item_id => $touches ) {
					$term_items[$parent][$item_id] = isset($term_items[$parent][$item_id]) ? ++$term_items[$parent][$item_id]: 1;
				}
			$child = $parent;
		}
	}

	// Transfer the touched cells
	foreach ( (array) $term_items as $id => $items )
		if ( isset($terms_by_id[$id]) )
			$terms_by_id[$id]->count = count($items);
}

//
// Default callbacks
//

/**
 * Will update term count based on object types of the current taxonomy.
 *
 * Private function for the default callback for post_tag and category
 * taxonomies.
 *
 * @package WordPress
 * @subpackage Taxonomy
 * @access private
 * @since 2.3.0
 * @uses $wpdb
 *
 * @param array $terms List of Term taxonomy IDs
 * @param object $taxonomy Current taxonomy object of terms
 */
function _update_post_term_count( $terms, $taxonomy ) {
	global $wpdb;

	$object_types = is_array($taxonomy->object_type) ? $taxonomy->object_type : array($taxonomy->object_type);
	$object_types = esc_sql($object_types);

	foreach ( (array) $terms as $term ) {
		$count = $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM $wpdb->term_relationships, $wpdb->posts WHERE $wpdb->posts.ID = $wpdb->term_relationships.object_id AND post_status = 'publish' AND post_type IN ('" . implode("', '", $object_types) . "') AND term_taxonomy_id = %d", $term ) );
		do_action( 'edit_term_taxonomy', $term, $taxonomy );
		$wpdb->update( $wpdb->term_taxonomy, compact( 'count' ), array( 'term_taxonomy_id' => $term ) );
		do_action( 'edited_term_taxonomy', $term, $taxonomy );
	}
}


/**
 * Generates a permalink for a taxonomy term archive.
 *
 * @since 2.5.0
 *
 * @uses apply_filters() Calls 'term_link' with term link and term object, and taxonomy parameters.
 * @uses apply_filters() For the post_tag Taxonomy, Calls 'tag_link' with tag link and tag ID as parameters.
 * @uses apply_filters() For the category Taxonomy, Calls 'category_link' filter on category link and category ID.
 *
 * @param object|int|string $term
 * @param string $taxonomy (optional if $term is object)
 * @return string HTML link to taxonomy term archive
 */
function get_term_link( $term, $taxonomy = '') {
	global $wp_rewrite;

	if ( !is_object($term) ) {
		if ( is_int($term) ) {
			$term = &get_term($term, $taxonomy);
		} else {
			$term = &get_term_by('slug', $term, $taxonomy);
		}
	}

	if ( !is_object($term) )
		$term = new WP_Error('invalid_term', __('Empty Term'));

	if ( is_wp_error( $term ) )
		return $term;

	$taxonomy = $term->taxonomy;

	$termlink = $wp_rewrite->get_extra_permastruct($taxonomy);

	$slug = $term->slug;
	$t = get_taxonomy($taxonomy);

	if ( empty($termlink) ) {
		if ( $t->query_var )
			$termlink = "?$t->query_var=$slug";
		else
			$termlink = "?taxonomy=$taxonomy&term=$slug";
		$termlink = home_url($termlink);
	} else {
		if ( $t->rewrite['hierarchical'] ) {
			$hierarchical_slugs = array();
			$ancestors = get_ancestors($term->term_id, $taxonomy);
			foreach ( (array)$ancestors as $ancestor ) {
				$ancestor_term = get_term($ancestor, $taxonomy);
				$hierarchical_slugs[] = $ancestor_term->slug;
			}
			$hierarchical_slugs = array_reverse($hierarchical_slugs);
			$hierarchical_slugs[] = $slug;
			$termlink = str_replace("%$taxonomy%", implode('/', $hierarchical_slugs), $termlink);
		} else {
			$termlink = str_replace("%$taxonomy%", $slug, $termlink);
		}
		$termlink = home_url( user_trailingslashit($termlink, 'category') );
	}
	// Back Compat filters.
	if ( 'post_tag' == $taxonomy )
		$termlink = apply_filters( 'tag_link', $termlink, $term->term_id );
	elseif ( 'category' == $taxonomy )
		$termlink = apply_filters( 'category_link', $termlink, $term->term_id );

	return apply_filters('term_link', $termlink, $term, $taxonomy);
}

/**
 * Display the taxonomies of a post with available options.
 *
 * This function can be used within the loop to display the taxonomies for a
 * post without specifying the Post ID. You can also use it outside the Loop to
 * display the taxonomies for a specific post.
 *
 * The available defaults are:
 * 'post' : default is 0. The post ID to get taxonomies of.
 * 'before' : default is empty string. Display before taxonomies list.
 * 'sep' : default is empty string. Separate every taxonomy with value in this.
 * 'after' : default is empty string. Display this after the taxonomies list.
 * 'template' : The template to use for displaying the taxonomy terms.
 *
 * @since 2.5.0
 * @uses get_the_taxonomies()
 *
 * @param array $args Override the defaults.
 */
function the_taxonomies($args = array()) {
	$defaults = array(
		'post' => 0,
		'before' => '',
		'sep' => ' ',
		'after' => '',
		'template' => '%s: %l.'
	);

	$r = wp_parse_args( $args, $defaults );
	extract( $r, EXTR_SKIP );

	echo $before . join($sep, get_the_taxonomies($post, $template)) . $after;
}

/**
 * Retrieve all taxonomies associated with a post.
 *
 * This function can be used within the loop. It will also return an array of
 * the taxonomies with links to the taxonomy and name.
 *
 * @since 2.5.0
 *
 * @param int $post Optional. Post ID or will use Global Post ID (in loop).
 * @param string $template Optional. The template to use for displaying the taxonomy terms.
 * @return array
 */
function get_the_taxonomies($post = 0, $template = '%s: %l.') {
	if ( is_int($post) )
		$post =& get_post($post);
	elseif ( !is_object($post) )
		$post =& $GLOBALS['post'];

	$taxonomies = array();

	if ( !$post )
		return $taxonomies;

	foreach ( get_object_taxonomies($post) as $taxonomy ) {
		$t = (array) get_taxonomy($taxonomy);
		if ( empty($t['label']) )
			$t['label'] = $taxonomy;
		if ( empty($t['args']) )
			$t['args'] = array();
		if ( empty($t['template']) )
			$t['template'] = $template;

		$terms = get_object_term_cache($post->ID, $taxonomy);
		if ( empty($terms) )
			$terms = wp_get_object_terms($post->ID, $taxonomy, $t['args']);

		$links = array();

		foreach ( $terms as $term )
			$links[] = "<a href='" . esc_attr( get_term_link($term) ) . "'>$term->name</a>";

		if ( $links )
			$taxonomies[$taxonomy] = wp_sprintf($t['template'], $t['label'], $links, $terms);
	}
	return $taxonomies;
}

/**
 * Retrieve all taxonomies of a post with just the names.
 *
 * @since 2.5.0
 * @uses get_object_taxonomies()
 *
 * @param int $post Optional. Post ID
 * @return array
 */
function get_post_taxonomies($post = 0) {
	$post =& get_post($post);

	return get_object_taxonomies($post);
}

/**
 * Determine if the given object is associated with any of the given terms.
 *
 * The given terms are checked against the object's terms' term_ids, names and slugs.
 * Terms given as integers will only be checked against the object's terms' term_ids.
 * If no terms are given, determines if object is associated with any terms in the given taxonomy.
 *
 * @since 2.7.0
 * @uses get_object_term_cache()
 * @uses wp_get_object_terms()
 *
 * @param int $object_id ID of the object (post ID, link ID, ...)
 * @param string $taxonomy Single taxonomy name
 * @param int|string|array $terms Optional.  Term term_id, name, slug or array of said
 * @return bool|WP_Error. WP_Error on input error.
 */
function is_object_in_term( $object_id, $taxonomy, $terms = null ) {
	if ( !$object_id = (int) $object_id )
		return new WP_Error( 'invalid_object', __( 'Invalid object ID' ) );

	$object_terms = get_object_term_cache( $object_id, $taxonomy );
	if ( empty( $object_terms ) )
		 $object_terms = wp_get_object_terms( $object_id, $taxonomy );

	if ( is_wp_error( $object_terms ) )
		return $object_terms;
	if ( empty( $object_terms ) )
		return false;
	if ( empty( $terms ) )
		return ( !empty( $object_terms ) );

	$terms = (array) $terms;

	if ( $ints = array_filter( $terms, 'is_int' ) )
		$strs = array_diff( $terms, $ints );
	else
		$strs =& $terms;

	foreach ( $object_terms as $object_term ) {
		if ( $ints && in_array( $object_term->term_id, $ints ) ) return true; // If int, check against term_id
		if ( $strs ) {
			if ( in_array( $object_term->term_id, $strs ) ) return true;
			if ( in_array( $object_term->name, $strs ) )    return true;
			if ( in_array( $object_term->slug, $strs ) )    return true;
		}
	}

	return false;
}

/**
 * Determine if the given object type is associated with the given taxonomy.
 *
 * @since 3.0.0
 * @uses get_object_taxonomies()
 *
 * @param string $object_type Object type string
 * @param string $taxonomy Single taxonomy name
 * @return bool True if object is associated with the taxonomy, otherwise false.
 */
function is_object_in_taxonomy($object_type, $taxonomy) {
	$taxonomies = get_object_taxonomies($object_type);

	if ( empty($taxonomies) )
		return false;

	if ( in_array($taxonomy, $taxonomies) )
		return true;

	return false;
}

/**
 * Get an array of ancestor IDs for a given object.
 *
 * @param int $object_id The ID of the object
 * @param string $object_type The type of object for which we'll be retrieving ancestors.
 * @return array of ancestors from lowest to highest in the hierarchy.
 */
function get_ancestors($object_id = 0, $object_type = '') {
	$object_id = (int) $object_id;

	$ancestors = array();

	if ( empty( $object_id ) ) {
		return apply_filters('get_ancestors', $ancestors, $object_id, $object_type);
	}

	if ( is_taxonomy_hierarchical( $object_type ) ) {
		$term = get_term($object_id, $object_type);
		while ( ! is_wp_error($term) && ! empty( $term->parent ) && ! in_array( $term->parent, $ancestors ) ) {
			$ancestors[] = (int) $term->parent;
			$term = get_term($term->parent, $object_type);
		}
	} elseif ( null !== get_post_type_object( $object_type ) ) {
		$object = get_post($object_id);
		if ( ! is_wp_error( $object ) && isset( $object->ancestors ) && is_array( $object->ancestors ) )
			$ancestors = $object->ancestors;
		else {
			while ( ! is_wp_error($object) && ! empty( $object->post_parent ) && ! in_array( $object->post_parent, $ancestors ) ) {
				$ancestors[] = (int) $object->post_parent;
				$object = get_post($object->post_parent);
			}
		}
	}

	return apply_filters('get_ancestors', $ancestors, $object_id, $object_type);
}

/**
 * Returns the term's parent's term_ID
 *
 * @since 3.1.0
 *
 * @param int $term_id
 * @param string $taxonomy
 *
 * @return int|bool false on error
 */
function wp_get_term_taxonomy_parent_id( $term_id, $taxonomy ) {
	$term = get_term( $term_id, $taxonomy );
	if ( !$term || is_wp_error( $term ) )
		return false;
	return (int) $term->parent;
}

/**
 * Checks the given subset of the term hierarchy for hierarchy loops.
 * Prevents loops from forming and breaks those that it finds.
 *
 * Attached to the wp_update_term_parent filter.
 *
 * @since 3.1.0
 * @uses wp_find_hierarchy_loop()
 *
 * @param int $parent term_id of the parent for the term we're checking.
 * @param int $term_id The term we're checking.
 * @param string $taxonomy The taxonomy of the term we're checking.
 *
 * @return int The new parent for the term.
 */
function wp_check_term_hierarchy_for_loops( $parent, $term_id, $taxonomy ) {
	// Nothing fancy here - bail
	if ( !$parent )
		return 0;

	// Can't be its own parent
	if ( $parent == $term_id )
		return 0;

	// Now look for larger loops

	if ( !$loop = wp_find_hierarchy_loop( 'wp_get_term_taxonomy_parent_id', $term_id, $parent, array( $taxonomy ) ) )
		return $parent; // No loop

	// Setting $parent to the given value causes a loop
	if ( isset( $loop[$term_id] ) )
		return 0;

	// There's a loop, but it doesn't contain $term_id.  Break the loop.
	foreach ( array_keys( $loop ) as $loop_member )
		wp_update_term( $loop_member, $taxonomy, array( 'parent' => 0 ) );

	return $parent;
}