WC_Order::set_address_prop PHP Method

    protected function set_address_prop($prop, $address = 'billing', $value)
    {
        if (array_key_exists($prop, $this->data[$address])) {
            if (true === $this->object_read) {
                if ($value !== $this->data[$address][$prop] || isset($this->changes[$address]) && array_key_exists($prop, $this->changes[$address])) {
                    $this->changes[$address][$prop] = $value;
                }
            } else {
                $this->data[$address][$prop] = $value;
            }
        }
    }