Revised function: Event_Tickets_PRO::payment_update()

public function payment_update( $postId, $eventId, $post ) {
    $paymentTypes = array('check' => '', 'cash' => '', 'invoice' => '');
    $requestParams = 'event_id=' . $eventId;

    // make it accept cash if free & assign a message
    if ( 2 == $post['EventBriteIsDonation'] ) {
        $requestParams .= '&accept_cash=1';
        $requestParams .= '&instructions_cash=' . urlencode( __( 'This event is free to attend', 'tribe-eventbrite' ) );
    } else {
        // otherwise loop through the payment methods as it's supposed to
        foreach( $paymentTypes as $key => $val ) {
            $onOff = $post['EventBritePayment_accept_' . $key];
            if ( $onOff ) $requestParams .= '&accept_' . $key . '=' . $onOff;
            $paymentTypes[$key] = $onOff;
        }
        foreach( $paymentTypes as $key => $val ) {
            if ( $val ) {
           $instructions = $post['EventBritePayment_instructions_'.$key];
           if ( $instructions ) $requestParams .= '&instructions_' . $key . '=' . urlencode( stripslashes( $instructions ) );
            }
        }

    // Online payment method is either/or (not both)
    $onlineMethod = $post['EventBritePayment_accept_online'];
    if ( !empty( $post['EventBritePayment_accept_online'] ) ) {
        switch( $onlineMethod ) {
        case 'paypal':
            $requestParams .= '&accept_paypal=1&paypal_email=' . $post['EventBritePayment_paypal_email'];
                    break;
          case 'google':
            $requestParams .= '&accept_google=1&google_merchant_id=' . $post['EventBritePayment_google_merchant_id'] . '&google_merchant_key=' . $post['EventBritePayment_google_merchant_key'];
           break;
        }
    }
}