Method: Get all tax classes for items in the cart.

Method: Check all cart items for errors.

Method: Check cart coupons for errors.

Method: Looks through cart items and checks the posts are not trashed or deleted.

Method: Looks through the cart to check each item is in stock. If not, add an error.

Method: Gets and formats a list of cart item data + variations for display on the frontend.

Method: Get cart items quantities – merged so we can do accurate stock checks on items across multiple lines.

Method: Checks if the cart is empty.

Method: Empties the cart and optionally the persistent cart too.

Method: Get number of items in the cart.