src/CartService.php
public function addItem($cartId, Product $product, $quantity = 1, array $options = [], array $extras = [], $note = null)
    {
        $cart = $this->getCartById($cartId);

        $cart->addItem($product, $quantity, $options, $extras, $note);

        $this->saveCart($cart);
    }
public function addItem($cartId, Product $product, $quantity = 1, array $options = [], array $extras = [], $note = null)
    {
        $cart = $this->getCartById($cartId);

        $cart->addItem($product, $quantity, $options, $extras, $note);

        $this->saveCart($cart);
    }
@param int     $cartId
@param Product $product
@param int     $quantity
@param array   $options array( optionSetId => optionId, ... )
@param array   $extras array( extraSetId_extraId, ... )
@param string  $note

@throws CartNotFoundException