PayPal\Api\Order::setReferenceId PHP Method

Identifier to the purchase unit associated with this object. Obsolete. Use one in cart_base.

public setReferenceId ( string $reference_id )
$reference_id	string

    public function setReferenceId($reference_id)
    {
        $this->reference_id = $reference_id;
        return $this;
    }

Order