public function getCardNumber() : ?string 
    {
        if ( ! $this->hasCardNumber()) {
            $this->setCardNumber($this->getDefaultCardNumber());
        }
        return $this->cardNumber;
    }
public function getCardNumber() : ?string 
    {
        if ( ! $this->hasCardNumber()) {
            $this->setCardNumber($this->getDefaultCardNumber());
        }
        return $this->cardNumber;
    }
public function getCardNumber ( ) : ? string { if ( ! $ this -> hasCardNumber ( ) ) { $ this -> setCardNumber ( $ this -> getDefaultCardNumber ( ) ) ; } return $ this -> cardNumber ; }
Get card number

If no "card number" value has been set, this method will
set and return a default "card number" value,
if any such value is available

@see getDefaultCardNumber()

@return string|null card number or null if no card number has been set
Get card number