src/Message/RestResponse.php
public function getCardReference()
    {
        if (isset($this->data['response']['token'])) {
            return $this->data['response']['token'];
        }
        if (isset($this->data['response']['card_token'])) {
            return $this->data['response']['card_token'];
        }
    }
public function getCardReference()
    {
        if (isset($this->data['response']['token'])) {
            return $this->data['response']['token'];
        }
        if (isset($this->data['response']['card_token'])) {
            return $this->data['response']['card_token'];
        }
    }
Get Card Reference

This is used after createCard or createCustomer to get the credit card token to be
used in future transactions.

@return string