Add Calculated Field (For Product)

Let’s create a new empty custom field:

1. Open section “Setup fields”

2. Open section “Products”

3. Click button “Add Field”

4. Type  custom meta key in text box (below the selects)

5. Fill “Column name”

5. Press button “Confirm”

In my example, I use “item_tax” as meta key on the screenshot

Then I moved new field  from right column to left column (list of exported fields),  pressed button  “Preview”  and see the zero values.

Then create a calculating function:

1. Close section “Setup fields” and open section “Misc Settings” (above it)
2. Mark checkbox “Custom PHP code to modify output”
3. Paste following draft function to the textarea

4. replace {FIELD} with your meta key (see 1st phase) .
5. replace $value = “text”;  with your code.

Parameters for the hook:

$value is string

$order is WC_Order  object

$item   is WC_Order_Item_Product object

$product is WC_Product  object

$item_meta is associative array

In this example, I use meta key “item_tax” and following code to calculate tax per item

I pressed button “Preview” and got  necessary values

If button “Preview” has no effect, there is an error in the code!

So mark checkbox “Enable debug output” to see the errors.