php update url variables

url.php

<?

function update_url($_data, $url = NULL){
	if (!$url) $url = "http://" . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];
	$_url = parse_url($url);

	if (isset($_url['query']) AND $_url['query']) parse_str($_url['query'], $_params);
	else $_params = array();
	$_updated_params = array_merge($_params, $_data);

	$new_url = $_url['scheme'] . '://' . $_url['host'] . $_url['path'];
	$new_url .= '?' . http_build_query($_updated_params);

	return $new_url;
}