Something

    public function getToBuild() {
      $stock_par = "SELECT p.name,
                           p.sku,
                           p.category,
                           p.ws_box_size,
                           p.choco,
                           s.par,
                           s.qty AS `have`,
                          s.par - s.qty AS `build`
                    FROM stock s
                      INNER JOIN products p ON s.sku=p.sku
                    WHERE s.par
                          AND s.qty < s.par
                    ORDER BY p.sku ASC";

      $store_backlog = "SELECT p.name,
                               p.sku,
                               p.category,
                               p.ws_box_size,
                               p.choco,
                               SUM(sod.par),
                               SUM(sod.have),
                               SUM(getOrder(sod.par, sod.have)) AS `build`
                        FROM store_orders_data sod
                          INNER JOIN products p ON (sod.sku=p.sku)
                          INNER JOIN store_orders so ON (so.orderid=sod.orderid)
                        WHERE
                              storeOrderStatus(getOrder(sod.par, sod.have), sod.ship, sod.receive) IN (0,1)
                              AND sod.receive=0
                              AND getOrder(sod.par, sod.have) NOT IN(0, sod.ship)
                              AND DATEDIFF(CURDATE(), so.date) < 20
                        GROUP BY p.sku
                        ORDER BY p.sku ASC";

      $sql = "($stock_par) UNION ($store_backlog)";
      $result = query($sql);
      $types = Array();
      while ($row = mysql_fetch_assoc($result))
        $types[$row['category']][] = $row;
      return $types;
    }
  }