Sum inside while loop

I have a table where are orders and table with orderrows and I need to fetch prices for both tables. I already have successfully fetched prices to orderrows, but I can't figure out how to sum up the row prices from $WMSOLPrices and add the value to variable $WMSOrderPrice. Any help? I know there are many other questions about the same problem, but I haven't got any help on those.

<?php
$WMSOrderLines = \WMS\Orders\OrdersDataMapper::getWMSLinesData($_REQUEST['id']);     
$WMSOLPrices = array();
$WMSOrderPrice = 0; // how to add sum from orderrow prices to this variable?
$sql = 'select wo.id as wms_orders_id, wl.id as wms_lines_id, tca.row_price as price from tms_cost_allocation tca, wms_orders wo, wms_lines wl where wo.id = :wms_orders_id and wo.id = wl.wms_orders_id and wl.quantity_packed > 0 and wl.order_lines_id = tca.order_lines_id and tca.row_price > 0';
            try {

            $query = DBCon::get(true)->prepare($sql);
            $query->bindValue(":wms_orders_id", $WMSOrder->id, PDO::PARAM_INT);
            $query->execute();
            while ($row = $query->fetch(PDO::FETCH_ASSOC)) {
                $WMSOLPrices[$row['wms_lines_id']] = $row;
            }
        }

        catch (PDOException $e) {
        ScriptNotification::logError("Exception while getting prices ",$e);
    }

    ?>

    <h1>Toimitustilaus</h1>

    <h2>Toimitustilaus</h2>
    <div style="padding-bottom: 10px;">
        <table class="admin-table">
            <thead class="admin-table-header">
            <tr> 
                <th>Toimitustilaus</th>
                <th>Rahtihinta</th>
            </tr>
            </thead>
            <tbody class="admin-table-body">
            <tr>
                <td>
                    <?php echo $WMSOrder->id; ?>
                <td>
                    <?php echo $WMSOrderPrice; ?>
                </td>
            </tr>
            </tbody>
        </table>
    </div>

    <h2>Toimitustilauksen rivit</h2>
    <div style="padding-bottom: 10px;">
        <table class="admin-table">
            <thead class="admin-table-header">
            <tr>
                <th>Toimitusrivi</th>
                <th>Tilausrivi</th>
                <th>Rivihinta</th>
            </tr>
            </thead>
            <tbody class="admin-table-body">
            <?php foreach($WMSOrderLines as $WMSLine) { ?>
                <tr>
                    <td><?php echo $WMSLine->id; ?></td>
                    <td><?php echo $WMSLine->order_lines_id; ?></td>
                    <td><?php if(isset($WMSOLPrices[$WMSLine->id])) { echo $WMSOLPrices[$WMSLine->id]['price']; }?></td>
                </tr>
            <?php } ?>
            </tbody>
        </table>
    </div>
    <?php
}`