$input['txnType'] = $this->retrieve('txn_type', 'String', FALSE);
$input['paymentStatus'] = $this->retrieve('payment_status', 'String', FALSE);
$input['invoice'] = $this->retrieve('invoice', 'String', TRUE);
$input['txnType'] = $this->retrieve('txn_type', 'String', FALSE);
$input['paymentStatus'] = $this->retrieve('payment_status', 'String', FALSE);
$input['invoice'] = $this->retrieve('invoice', 'String', TRUE);