Custom field to Variable

-- HikaShop version -- : 3.5.6
-- Joomla version -- : 3.5.2
-- PHP version -- : 5.4
-- Error-message(debug-mod must be tuned on) -- : Get custom fields to variable

HI i have create a custom field in the product page call 'principal' which would be 1 to 3 (number) the idea of that field is that i could evaluate with php code using if and is that field is 1 the cell background would be green, else it would be red.

My problem is that i don't know how to get the value of the that custom field in the view listing_table

would you help me please i just need to transfer the value of the fiel to a varibale into php code

I am develoment to reports in backend in the view Show php is just a query so simple but i need get the order id or the order number, how could i transfer the code if to a pho variabl call $order_yo or wahtever