Craft\FormBuilder2_FieldService::saveLabel PHP Method

    public function saveLabel(FormBuilder2_FieldModel $label)
    {
        $isExisting = false;
        $record = null;
        if (is_int($label->id)) {
            $record = FormBuilder2_FieldRecord::model()->findById($label->id);
            if ($record) {
                $isExisting = true;
            } else {
                throw new Exception(Craft::t('No label exists with the ID “{id}”.', array('id' => $label->id)));
            }
        } else {
            $record = FormBuilder2_FieldRecord::model()->findByAttributes(array('fieldId' => $label->fieldId, 'fieldLayoutId' => $label->fieldLayoutId));
            if ($record) {
                $isExisting = true;
            } else {
                $record = new FormBuilder2_FieldRecord();
            }
        }
        $field = craft()->fields->getFieldById($label->fieldId);
        $layout = craft()->fields->getLayoutById($label->fieldLayoutId);
        if (!$field) {
            throw new Exception(Craft::t('No field exists with the ID “{id}”.', array('id' => $label->fieldId)));
        }
        if (!$layout) {
            throw new Exception(Craft::t('No field layout exists with the ID “{id}”.', array('id' => $label->fieldLayoutId)));
        }
        $record->fieldId = $label->fieldId;
        $record->fieldLayoutId = $label->fieldLayoutId;
        $record->template = $label->template;
        $record->validate();
        $label->addErrors($record->getErrors());
        $success = !$label->hasErrors();
        if ($success) {
            $event = new Event($this, array('label' => $label, 'isNewCustomField' => !$isExisting));
            $this->onBeforeSaveLabel($event);
            if ($event->performAction) {
                $transaction = craft()->db->getCurrentTransaction() ? false : craft()->db->beginTransaction();
                try {
                    $record->save(false);
                    $label->id = $record->id;
                    if ($transaction) {
                        $transaction->commit();
                    }
                } catch (\Exception $e) {
                    if ($transaction) {
                        $transaction->rollback();
                    }
                    throw $e;
                }
                $this->onSaveLabel(new Event($this, array('label' => $label, 'isNewCustomField' => !$isExisting)));
            }
        }
        return $success;
    }