* @return CRM_Core_Payment
* @throws \CRM_Core_Exception
*/
- public static function &singleton($mode = 'test', &$paymentProcessor, &$paymentForm = NULL, $force = FALSE) {
+ public static function singleton($mode = 'test', &$paymentProcessor, &$paymentForm = NULL, $force = FALSE) {
// make sure paymentProcessor is not empty
// CRM-7424
if (empty($paymentProcessor)) {