public function setMerchantData($data, $alreadyEncoded = false) {
		if (!$alreadyEncoded) {
			$data = base64_encode($data);
		}
		if (strlen($data) > 255) {
			throw new Exception("Merchant data can not be longer than 255 characters after base64 encoding.");
		}
		$this->merchantData = $data;
		return $this;
	}