Multiply fields (from another table)

Hello! I am trying to calculate fields (multiply) from another table.

I want to multiply unit price and quantity.

Unit price is coming from the Product Inventory Table, while Quantity is from the Order table.

I calculated it using run time, but I just can’t figure out how to call or return the data from another table.

Here’s my code snippet:


public function getTotal()


$prod = ‘productinventory.price’;

    return ($this->$prod * $this->num_items);


I called it using: (view.php -> Order)


        'attribute' => 'amount',

        'value' => $model->getTotal(),


I am getting this error: Getting unknown property: backend\models\Order::productinventory.price

num_items is the quantity

while productinventory.price is the price coming from Product Inventory Table.