WP_List_Util::sort

	 *                                    of multiple orderby fields as $orderby => $order.
	 * @param string       $order         Optional. Either 'ASC' or 'DESC'. Only used if $orderby
	 *                                    is a string.
	 * @param bool         $preserve_keys Optional. Whether to preserve keys. Default false.
	 * @return array The sorted array.
	 */
	public function sort( $orderby = array(), $order = 'ASC', $preserve_keys = false ) {
		if ( empty( $orderby ) ) {
			return $this->output;
		}

		if ( is_string( $orderby ) ) {
			$orderby = array( $orderby => $order );
		}

		foreach ( $orderby as $field => $direction ) {
			$orderby[ $field ] = 'DESC' === strtoupper( $direction ) ? 'DESC' : 'ASC';
		}

		$this->orderby = $orderby;

		if ( $preserve_keys ) {
			uasort( $this->output, array( $this, 'sort_callback' ) );
		} else {
			usort( $this->output, array( $this, 'sort_callback' ) );