.
	 *
	 * @since 2.7.0
	 *
	 * @param array $elements Elements to list.
	 * @return int Number of root elements.
	 */
	public function get_number_of_root_elements( $elements ) {
		$num          = 0;
		$parent_field = $this->db_fields['parent'];

		foreach ( $elements as $e ) {
			if ( empty( $e->$parent_field ) ) {
				++$num;
			}
		}
		return $num;
	}

	/**
	 * Unsets all the children for a given top level element.
	 *
	 * @since 2.7.0
	 *
	 * @param object $element           The top level element.
	 * @param array  $children_elements The children elements.
	 */
	public function unset_children( $element, &$children_elements ) {
		if ( ! $element || ! $children_elements ) {
			return;
		}

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

		if ( ! empty( $children_elements[ $id ] ) && is_array( $children_elements[ $id ] ) ) {
			foreach ( (array) $children_elements[ $id ] as $child ) {
				$this->unset_children( $child, $children_elements );
			}
		}

		unset( $children_elements[ $id ] );
	}
}
<![CDATA[$data]]></response_data>";
		}

		$s = '';
		if ( is_array( $parsed_args['supplemental'] ) ) {
			foreach ( $parsed_args['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;
	}

	/**
	 * Display XML formatted responses.
	 *
	 * Sets the content type header to text/xml.
	 *
	 * @since 2.1.0
	 */
	public function send() {
		header( 'Content-Type: text/xml; charset=' . get_option( 'blog_charset' ) );
		echo "<?xml version='1.0' encoding='" . get_option( 'blog_charset' ) . "' standalone='yes'?><wp_ajax>";
		foreach ( (array) $this->responses as $response ) {
			echo $response;
		}
		echo '</wp_ajax>';
		if ( wp_doing_ajax() ) {
			wp_die();
		} else {
			die();
		}
	}
}