WordPress/wp-includes/classes.php

<?php

class WP {
	var $public_query_vars = array('m', 'p', 'posts', 'w', 'cat', 'withcomments', 'withoutcomments', 's', 'search', 'exact', 'sentence', 'debug', 'calendar', 'page', 'paged', 'more', 'tb', 'pb', 'author', 'order', 'orderby', 'year', 'monthnum', 'day', 'hour', 'minute', 'second', 'name', 'category_name', 'tag', 'feed', 'author_name', 'static', 'pagename', 'page_id', 'error', 'comments_popup', 'attachment', 'attachment_id', 'subpost', 'subpost_id', 'preview', 'robots', 'taxonomy', 'term');

	var $private_query_vars = array('offset', 'posts_per_page', 'posts_per_archive_page', 'what_to_show', 'showposts', 'nopaging', 'post_type', 'post_status', 'category__in', 'category__not_in', 'category__and', 'tag__in', 'tag__not_in', 'tag__and', 'tag_slug__in', 'tag_slug__and', 'tag_id', 'post_mime_type', 'perm');
	var $extra_query_vars = array();

	var $query_vars;
	var $query_string;
	var $request;
	var $matched_rule;
	var $matched_query;
	var $did_permalink = false;

	function add_query_var($qv) {
		if ( !in_array($qv, $this->public_query_vars) )
			$this->public_query_vars[] = $qv;
	}

	function set_query_var($key, $value) {
		$this->query_vars[$key] = $value;
	}

	function parse_request($extra_query_vars = '') {
		global $wp_rewrite;

		$this->query_vars = array();
		$taxonomy_query_vars = array();

		if ( is_array($extra_query_vars) )
			$this->extra_query_vars = & $extra_query_vars;
		else if (! empty($extra_query_vars))
			parse_str($extra_query_vars, $this->extra_query_vars);

		// Process PATH_INFO, REQUEST_URI, and 404 for permalinks.

		// Fetch the rewrite rules.
		$rewrite = $wp_rewrite->wp_rewrite_rules();

		if (! empty($rewrite)) {
			// If we match a rewrite rule, this will be cleared.
			$error = '404';
			$this->did_permalink = true;

			if ( isset($_SERVER['PATH_INFO']) )
				$pathinfo = $_SERVER['PATH_INFO'];
			else
				$pathinfo = '';
			$pathinfo_array = explode('?', $pathinfo);
			$pathinfo = str_replace("%", "%25", $pathinfo_array[0]);
			$req_uri = $_SERVER['REQUEST_URI'];
			$req_uri_array = explode('?', $req_uri);
			$req_uri = $req_uri_array[0];
			$self = $_SERVER['PHP_SELF'];
			$home_path = parse_url(get_option('home'));
			if ( isset($home_path['path']) )
				$home_path = $home_path['path'];
			else
				$home_path = '';
			$home_path = trim($home_path, '/');

			// Trim path info from the end and the leading home path from the
			// front.  For path info requests, this leaves us with the requesting
			// filename, if any.  For 404 requests, this leaves us with the
			// requested permalink.
			$req_uri = str_replace($pathinfo, '', rawurldecode($req_uri));
			$req_uri = trim($req_uri, '/');
			$req_uri = preg_replace("|^$home_path|", '', $req_uri);
			$req_uri = trim($req_uri, '/');
			$pathinfo = trim($pathinfo, '/');
			$pathinfo = preg_replace("|^$home_path|", '', $pathinfo);
			$pathinfo = trim($pathinfo, '/');
			$self = trim($self, '/');
			$self = preg_replace("|^$home_path|", '', $self);
			$self = trim($self, '/');

			// The requested permalink is in $pathinfo for path info requests and
			//  $req_uri for other requests.
			if ( ! empty($pathinfo) && !preg_match('|^.*' . $wp_rewrite->index . '$|', $pathinfo) ) {
				$request = $pathinfo;
			} else {
				// If the request uri is the index, blank it out so that we don't try to match it against a rule.
				if ( $req_uri == $wp_rewrite->index )
					$req_uri = '';
				$request = $req_uri;
			}

			$this->request = $request;

			// Look for matches.
			$request_match = $request;
			foreach ($rewrite as $match => $query) {
				// Don't try to match against AtomPub calls
				if ( $req_uri == 'wp-app.php' )
					break;

				// If the requesting file is the anchor of the match, prepend it
				// to the path info.
				if ((! empty($req_uri)) && (strpos($match, $req_uri) === 0) && ($req_uri != $request)) {
					$request_match = $req_uri . '/' . $request;
				}

				if (preg_match("!^$match!", $request_match, $matches) ||
					preg_match("!^$match!", urldecode($request_match), $matches)) {
					// Got a match.
					$this->matched_rule = $match;

					// Trim the query of everything up to the '?'.
					$query = preg_replace("!^.+\?!", '', $query);

					// Substitute the substring matches into the query.
					eval("\$query = \"" . addslashes($query) . "\";");
					$this->matched_query = $query;

					// Parse the query.
					parse_str($query, $perma_query_vars);

					// If we're processing a 404 request, clear the error var
					// since we found something.
					if (isset($_GET['error']))
						unset($_GET['error']);

					if (isset($error))
						unset($error);

					break;
				}
			}

			// If req_uri is empty or if it is a request for ourself, unset error.
			if (empty($request) || $req_uri == $self || strpos($_SERVER['PHP_SELF'], 'wp-admin/') !== false) {
				if (isset($_GET['error']))
					unset($_GET['error']);

				if (isset($error))
					unset($error);

				if (isset($perma_query_vars) && strpos($_SERVER['PHP_SELF'], 'wp-admin/') !== false)
					unset($perma_query_vars);

				$this->did_permalink = false;
			}
		}

		$this->public_query_vars = apply_filters('query_vars', $this->public_query_vars);

		foreach ( $GLOBALS['wp_taxonomies'] as $taxonomy => $t )
			if ( isset($t->query_var) )
				$taxonomy_query_vars[$t->query_var] = $taxonomy;

		for ($i=0; $i<count($this->public_query_vars); $i += 1) {
			$wpvar = $this->public_query_vars[$i];
			if (isset($this->extra_query_vars[$wpvar]))
				$this->query_vars[$wpvar] = $this->extra_query_vars[$wpvar];
			elseif (isset($GLOBALS[$wpvar]))
				$this->query_vars[$wpvar] = $GLOBALS[$wpvar];
			elseif (!empty($_POST[$wpvar]))
				$this->query_vars[$wpvar] = $_POST[$wpvar];
			elseif (!empty($_GET[$wpvar]))
				$this->query_vars[$wpvar] = $_GET[$wpvar];
			elseif (!empty($perma_query_vars[$wpvar]))
				$this->query_vars[$wpvar] = $perma_query_vars[$wpvar];

			if ( !empty( $this->query_vars[$wpvar] ) ) {
				$this->query_vars[$wpvar] = (string) $this->query_vars[$wpvar];
				if ( in_array( $wpvar, $taxonomy_query_vars ) ) {
					$this->query_vars['taxonomy'] = $taxonomy_query_vars[$wpvar];
					$this->query_vars['term'] = $this->query_vars[$wpvar];
				}
			}
		}

		foreach ($this->private_query_vars as $var) {
			if (isset($this->extra_query_vars[$var]))
				$this->query_vars[$var] = $this->extra_query_vars[$var];
			elseif (isset($GLOBALS[$var]) && '' != $GLOBALS[$var])
				$this->query_vars[$var] = $GLOBALS[$var];
		}

		if ( isset($error) )
			$this->query_vars['error'] = $error;

		$this->query_vars = apply_filters('request', $this->query_vars);

		do_action_ref_array('parse_request', array(&$this));
	}

	function send_headers() {
		@header('X-Pingback: '. get_bloginfo('pingback_url'));
		if ( is_user_logged_in() )
			nocache_headers();
		if ( !empty($this->query_vars['error']) && '404' == $this->query_vars['error'] ) {
			status_header( 404 );
			if ( !is_user_logged_in() )
				nocache_headers();
			@header('Content-Type: ' . get_option('html_type') . '; charset=' . get_option('blog_charset'));
		} else if ( empty($this->query_vars['feed']) ) {
			@header('Content-Type: ' . get_option('html_type') . '; charset=' . get_option('blog_charset'));
		} else {
			// We're showing a feed, so WP is indeed the only thing that last changed
			if ( !empty($this->query_vars['withcomments'])
				|| ( empty($this->query_vars['withoutcomments'])
					&& ( !empty($this->query_vars['p'])
						|| !empty($this->query_vars['name'])
						|| !empty($this->query_vars['page_id'])
						|| !empty($this->query_vars['pagename'])
						|| !empty($this->query_vars['attachment'])
						|| !empty($this->query_vars['attachment_id'])
					)
				)
			)
				$wp_last_modified = mysql2date('D, d M Y H:i:s', get_lastcommentmodified('GMT'), 0).' GMT';
			else
				$wp_last_modified = mysql2date('D, d M Y H:i:s', get_lastpostmodified('GMT'), 0).' GMT';
			$wp_etag = '"' . md5($wp_last_modified) . '"';
			@header("Last-Modified: $wp_last_modified");
			@header("ETag: $wp_etag");

			// Support for Conditional GET
			if (isset($_SERVER['HTTP_IF_NONE_MATCH']))
				$client_etag = stripslashes(stripslashes($_SERVER['HTTP_IF_NONE_MATCH']));
			else $client_etag = false;

			$client_last_modified = empty($_SERVER['HTTP_IF_MODIFIED_SINCE']) ? '' : trim($_SERVER['HTTP_IF_MODIFIED_SINCE']);
			// If string is empty, return 0. If not, attempt to parse into a timestamp
			$client_modified_timestamp = $client_last_modified ? strtotime($client_last_modified) : 0;

			// Make a timestamp for our most recent modification...
			$wp_modified_timestamp = strtotime($wp_last_modified);

			if ( ($client_last_modified && $client_etag) ?
					 (($client_modified_timestamp >= $wp_modified_timestamp) && ($client_etag == $wp_etag)) :
					 (($client_modified_timestamp >= $wp_modified_timestamp) || ($client_etag == $wp_etag)) ) {
				status_header( 304 );
				exit;
			}
		}

		do_action_ref_array('send_headers', array(&$this));
	}

	function build_query_string() {
		$this->query_string = '';
		foreach (array_keys($this->query_vars) as $wpvar) {
			if ( '' != $this->query_vars[$wpvar] ) {
				$this->query_string .= (strlen($this->query_string) < 1) ? '' : '&';
				if ( !is_scalar($this->query_vars[$wpvar]) ) // Discard non-scalars.
					continue;
				$this->query_string .= $wpvar . '=' . rawurlencode($this->query_vars[$wpvar]);
			}
		}

		// query_string filter deprecated.  Use request filter instead.
		if ( has_filter('query_string') ) {  // Don't bother filtering and parsing if no plugins are hooked in.
			$this->query_string = apply_filters('query_string', $this->query_string);
			parse_str($this->query_string, $this->query_vars);
		}
	}

	function register_globals() {
		global $wp_query;
		// Extract updated query vars back into global namespace.
		foreach ($wp_query->query_vars as $key => $value) {
			$GLOBALS[$key] = $value;
		}

		$GLOBALS['query_string'] = & $this->query_string;
		$GLOBALS['posts'] = & $wp_query->posts;
		$GLOBALS['post'] = & $wp_query->post;
		$GLOBALS['request'] = & $wp_query->request;

		if ( is_single() || is_page() ) {
			$GLOBALS['more'] = 1;
			$GLOBALS['single'] = 1;
		}
	}

	function init() {
		wp_get_current_user();
	}

	function query_posts() {
		global $wp_the_query;
		$this->build_query_string();
		$wp_the_query->query($this->query_vars);
 	}

	function handle_404() {
		global $wp_query;
		// Issue a 404 if a permalink request doesn't match any posts.  Don't
		// issue a 404 if one was already issued, if the request was a search,
		// or if the request was a regular query string request rather than a
		// permalink request.
		if ( (0 == count($wp_query->posts)) && !is_404() && !is_search() && ( $this->did_permalink || (!empty($_SERVER['QUERY_STRING']) && (false === strpos($_SERVER['REQUEST_URI'], '?'))) ) ) {
			$wp_query->set_404();
			status_header( 404 );
			nocache_headers();
		}	elseif( is_404() != true ) {
			status_header( 200 );
		}
	}

	function main($query_args = '') {
		$this->init();
		$this->parse_request($query_args);
		$this->send_headers();
		$this->query_posts();
		$this->handle_404();
		$this->register_globals();
		do_action_ref_array('wp', array(&$this));
	}

	function WP() {
		// Empty.
	}
}

class WP_Error {
	var $errors = array();
	var $error_data = array();

	function WP_Error($code = '', $message = '', $data = '') {
		if ( empty($code) )
			return;

		$this->errors[$code][] = $message;

		if ( ! empty($data) )
			$this->error_data[$code] = $data;
	}

	function get_error_codes() {
		if ( empty($this->errors) )
			return array();

		return array_keys($this->errors);
	}

	function get_error_code() {
		$codes = $this->get_error_codes();

		if ( empty($codes) )
			return '';

		return $codes[0];
	}

	function get_error_messages($code = '') {
		// Return all messages if no code specified.
		if ( empty($code) ) {
			$all_messages = array();
			foreach ( $this->errors as $code => $messages )
				$all_messages = array_merge($all_messages, $messages);

			return $all_messages;
		}

		if ( isset($this->errors[$code]) )
			return $this->errors[$code];
		else
			return array();
	}

	function get_error_message($code = '') {
		if ( empty($code) )
			$code = $this->get_error_code();
		$messages = $this->get_error_messages($code);
		if ( empty($messages) )
			return '';
		return $messages[0];
	}

	function get_error_data($code = '') {
		if ( empty($code) )
			$code = $this->get_error_code();

		if ( isset($this->error_data[$code]) )
			return $this->error_data[$code];
		return null;
	}

	function add($code, $message, $data = '') {
		$this->errors[$code][] = $message;
		if ( ! empty($data) )
			$this->error_data[$code] = $data;
	}

	function add_data($data, $code = '') {
		if ( empty($code) )
			$code = $this->get_error_code();

		$this->error_data[$code] = $data;
	}
}

function is_wp_error($thing) {
	if ( is_object($thing) && is_a($thing, 'WP_Error') )
		return true;
	return false;
}

/*
 * A class for displaying various tree-like structures.
 * Extend the Walker class to use it, see examples at the bottom
 */
class Walker {
	var $tree_type;
	var $db_fields;

	//abstract callbacks
	function start_lvl(&$output) {}
	function end_lvl(&$output)   {}
	function start_el(&$output)  {}
	function end_el(&$output)    {}

	/*
 	 * display one element if the element doesn't have any children
 	 * otherwise, display the element and its children
 	 */
	function display_element( $element, &$children_elements, $max_depth, $depth=0, $args, &$output ) {

		if ( !$element )
			return;

		$id_field = $this->db_fields['id'];

		//display this element
		$cb_args = array_merge( array(&$output, $element, $depth), $args);
		call_user_func_array(array(&$this, 'start_el'), $cb_args);

		$id = $element->$id_field; 
		
		// descend only the depth is right and there are chilrens for this element
		if ( ($max_depth == 0 || $max_depth > $depth+1 ) && isset( $children_elements[$id]) ) { 

			foreach( $children_elements[ $id ] as $child ){
				
				if ( !isset($newlevel) ) {
					$newlevel = true;
					//start the child delimiter
					$cb_args = array_merge( array(&$output, $depth), $args);
					call_user_func_array(array(&$this, 'start_lvl'), $cb_args);
				}
				$this->display_element( $child, $children_elements, $max_depth, $depth + 1, $args, $output );
			}
			unset( $children_elements[ $id ] ); 
		}

		if ( isset($newlevel) && $newlevel ){
			//end the child delimiter
			$cb_args = array_merge( array(&$output, $depth), $args);
			call_user_func_array(array(&$this, 'end_lvl'), $cb_args);
		}

		//end this element
		$cb_args = array_merge( array(&$output, $element, $depth), $args);
		call_user_func_array(array(&$this, 'end_el'), $cb_args);
	}

	/*
 	* displays array of elements hierarchically
 	* it is a generic function which does not assume any existing order of elements
 	* max_depth = -1 means flatly display every element
 	* max_depth = 0  means display all levels
 	* max_depth > 0  specifies the number of display levels.
 	*/
	function walk( $elements, $max_depth) {

		$args = array_slice(func_get_args(), 2);
		$output = '';

		if ($max_depth < -1) //invalid parameter
			return $output;

		if (empty($elements)) //nothing to walk
			return $output;

		$id_field = $this->db_fields['id'];
		$parent_field = $this->db_fields['parent'];

		// flat display
		if ( -1 == $max_depth ) {
			$empty_array = array();
			foreach ( $elements as $e )
				$this->display_element( $e, $empty_array, 1, 0, $args, $output );
			return $output;
		}

		/*
		 * need to display in hierarchical order
		 * seperate elements into two buckets: top level and children elements
		 * children_elements is two dimensional array, eg. 
		 * children_elements[10][] contains all sub-elements whose parent is 10. 
		 */
		$top_level_elements = array();
		$children_elements  = array();
		foreach ( $elements as $e) {
			if ( 0 == $e->$parent_field )
				$top_level_elements[] = $e;
			else
				$children_elements[ $e->$parent_field ][] = $e;
		}

		/*
		 * when none of the elements is top level
		 * assume the first one must be root of the sub elements
		 */
		if ( empty($top_level_elements) ) {

			$root = $elements[0];
			
			$top_level_elements = array();
			$children_elements  = array();
			foreach ( $elements as $e) {
				if ( $root->$parent_field == $e->$parent_field )
					$top_level_elements[] = $e;
				else
					$children_elements[ $e->$parent_field ][] = $e;
			}
		}

		foreach ( $top_level_elements as $e )
			$this->display_element( $e, $children_elements, $max_depth, 0, $args, $output );

		/*
		* if we are displaying all levels, and remaining children_elements is not empty,
		* then we got orphans, which should be displayed regardless
	 	*/
		if ( ( $max_depth == 0 ) && sizeof( $children_elements ) > 0 ) {
			$empty_array = array();
			foreach ( $children_elements as $orphans )
				foreach( $orphans as $op )
					$this->display_element( $op, $empty_array, 1, 0, $args, $output );
		 }
		 
		 return $output;
	}
}

class Walker_Page extends Walker {
	var $tree_type = 'page';
	var $db_fields = array ('parent' => 'post_parent', 'id' => 'ID'); //TODO: decouple this

	function start_lvl(&$output, $depth) {
		$indent = str_repeat("\t", $depth);
		$output .= "\n$indent<ul>\n";
	}

	function end_lvl(&$output, $depth) {
		$indent = str_repeat("\t", $depth);
		$output .= "$indent</ul>\n";
	}

	function start_el(&$output, $page, $depth, $current_page, $args) {
		if ( $depth )
			$indent = str_repeat("\t", $depth);
		else
			$indent = '';

		extract($args, EXTR_SKIP);
		$css_class = 'page_item page-item-'.$page->ID;
		if ( !empty($current_page) ) {
			$_current_page = get_page( $current_page );
			if ( in_array($page->ID, (array) $_current_page->ancestors) )
				$css_class .= ' current_page_ancestor';
			if ( $page->ID == $current_page )
				$css_class .= ' current_page_item';
			elseif ( $_current_page && $page->ID == $_current_page->post_parent )
				$css_class .= ' current_page_parent';
		}

		$output .= $indent . '<li class="' . $css_class . '"><a href="' . get_page_link($page->ID) . '" title="' . attribute_escape(apply_filters('the_title', $page->post_title)) . '">' . apply_filters('the_title', $page->post_title) . '</a>';

		if ( !empty($show_date) ) {
			if ( 'modified' == $show_date )
				$time = $page->post_modified;
			else
				$time = $page->post_date;

			$output .= " " . mysql2date($date_format, $time);
		}
	}

	function end_el(&$output, $page, $depth) {
		$output .= "</li>\n";
	}

}

class Walker_PageDropdown extends Walker {
	var $tree_type = 'page';
	var $db_fields = array ('parent' => 'post_parent', 'id' => 'ID'); //TODO: decouple this

	function start_el(&$output, $page, $depth, $args) {
		$pad = str_repeat('&nbsp;', $depth * 3);

		$output .= "\t<option value=\"$page->ID\"";
		if ( $page->ID == $args['selected'] )
			$output .= ' selected="selected"';
		$output .= '>';
		$title = wp_specialchars($page->post_title);
		$output .= "$pad$title";
		$output .= "</option>\n";
	}
}

class Walker_Category extends Walker {
	var $tree_type = 'category';
	var $db_fields = array ('parent' => 'parent', 'id' => 'term_id'); //TODO: decouple this

	function start_lvl(&$output, $depth, $args) {
		if ( 'list' != $args['style'] )
			return;

		$indent = str_repeat("\t", $depth);
		$output .= "$indent<ul class='children'>\n";
	}

	function end_lvl(&$output, $depth, $args) {
		if ( 'list' != $args['style'] )
			return;

		$indent = str_repeat("\t", $depth);
		$output .= "$indent</ul>\n";
	}

	function start_el(&$output, $category, $depth, $args) {
		extract($args);

		$cat_name = attribute_escape( $category->name);
		$cat_name = apply_filters( 'list_cats', $cat_name, $category );
		$link = '<a href="' . get_category_link( $category->term_id ) . '" ';
		if ( $use_desc_for_title == 0 || empty($category->description) )
			$link .= 'title="' . sprintf(__( 'View all posts filed under %s' ), $cat_name) . '"';
		else
			$link .= 'title="' . attribute_escape( apply_filters( 'category_description', $category->description, $category )) . '"';
		$link .= '>';
		$link .= $cat_name . '</a>';

		if ( (! empty($feed_image)) || (! empty($feed)) ) {
			$link .= ' ';

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

			$link .= '<a href="' . get_category_feed_link($category->term_id, $feed_type) . '"';

			if ( empty($feed) )
				$alt = ' alt="' . sprintf(__( 'Feed for all posts filed under %s' ), $cat_name ) . '"';
			else {
				$title = ' title="' . $feed . '"';
				$alt = ' alt="' . $feed . '"';
				$name = $feed;
				$link .= $title;
			}

			$link .= '>';

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

		if ( isset($show_count) && $show_count )
			$link .= ' (' . intval($category->count) . ')';

		if ( isset($show_date) && $show_date ) {
			$link .= ' ' . gmdate('Y-m-d', $category->last_update_timestamp);
		}

		if ( isset($current_category) && $current_category )
			$_current_category = get_category( $current_category );

		if ( 'list' == $args['style'] ) {
			$output .= "\t<li";
			$class = 'cat-item cat-item-'.$category->term_id;
			if ( isset($current_category) && $current_category && ($category->term_id == $current_category) )
				$class .=  ' current-cat';
			elseif ( isset($_current_category) && $_current_category && ($category->term_id == $_current_category->parent) )
				$class .=  ' current-cat-parent';
			$output .=  ' class="'.$class.'"';
			$output .= ">$link\n";
		} else {
			$output .= "\t$link<br />\n";
		}
	}

	function end_el(&$output, $page, $depth, $args) {
		if ( 'list' != $args['style'] )
			return;

		$output .= "</li>\n";
	}

}

class Walker_CategoryDropdown extends Walker {
	var $tree_type = 'category';
	var $db_fields = array ('parent' => 'parent', 'id' => 'term_id'); //TODO: decouple this

	function start_el(&$output, $category, $depth, $args) {
		$pad = str_repeat('&nbsp;', $depth * 3);

		$cat_name = apply_filters('list_cats', $category->name, $category);
		$output .= "\t<option value=\"".$category->term_id."\"";
		if ( $category->term_id == $args['selected'] )
			$output .= ' selected="selected"';
		$output .= '>';
		$output .= $pad.$cat_name;
		if ( $args['show_count'] )
			$output .= '&nbsp;&nbsp;('. $category->count .')';
		if ( $args['show_last_update'] ) {
			$format = 'Y-m-d';
			$output .= '&nbsp;&nbsp;' . gmdate($format, $category->last_update_timestamp);
		}
		$output .= "</option>\n";
	}
}

class WP_Ajax_Response {
	var $responses = array();

	function WP_Ajax_Response( $args = '' ) {
		if ( !empty($args) )
			$this->add($args);
	}

	// a WP_Error object can be passed in 'id' or 'data'
	function add( $args = '' ) {
		$defaults = array(
			'what' => 'object', 'action' => false,
			'id' => '0', 'old_id' => false,
			'position' => 1, // -1 = top, 1 = bottom, html ID = after, -html ID = before
			'data' => '', 'supplemental' => array()
		);

		$r = wp_parse_args( $args, $defaults );
		extract( $r, EXTR_SKIP );
		$position = preg_replace( '/[^a-z0-9:_-]/i', '', $position );

		if ( is_wp_error($id) ) {
			$data = $id;
			$id = 0;
		}

		$response = '';
		if ( is_wp_error($data) ) {
			foreach ( $data->get_error_codes() as $code ) {
				$response .= "<wp_error code='$code'><![CDATA[" . $data->get_error_message($code) . "]]></wp_error>";
				if ( !$error_data = $data->get_error_data($code) )
					continue;
				$class = '';
				if ( is_object($error_data) ) {
					$class = ' class="' . get_class($error_data) . '"';
					$error_data = get_object_vars($error_data);
				}

				$response .= "<wp_error_data code='$code'$class>";

				if ( is_scalar($error_data) ) {
					$response .= "<![CDATA[$error_data]]>";
				} elseif ( is_array($error_data) ) {
					foreach ( $error_data as $k => $v )
						$response .= "<$k><![CDATA[$v]]></$k>";
				}

				$response .= "</wp_error_data>";
			}
		} else {
			$response = "<response_data><![CDATA[$data]]></response_data>";
		}

		$s = '';
		if ( (array) $supplemental ) {
			foreach ( $supplemental as $k => $v )
				$s .= "<$k><![CDATA[$v]]></$k>";
			$s = "<supplemental>$s</supplemental>";
		}

		if ( false === $action )
			$action = $_POST['action'];

		$x = '';
		$x .= "<response action='{$action}_$id'>"; // The action attribute in the xml output is formatted like a nonce action
		$x .=	"<$what id='$id' " . ( false === $old_id ? '' : "old_id='$old_id' " ) . "position='$position'>";
		$x .=		$response;
		$x .=		$s;
		$x .=	"</$what>";
		$x .= "</response>";

		$this->responses[] = $x;
		return $x;
	}

	function send() {
		header('Content-Type: text/xml');
		echo "<?xml version='1.0' standalone='yes'?><wp_ajax>";
		foreach ( $this->responses as $response )
			echo $response;
		echo '</wp_ajax>';
		die();
	}
}

?>