getFieldValues.php

    public function getFieldValues(BaseElementModel $entry, $fields = null)
    {
        foreach ($entry->fieldLayout->fields as $fieldLayoutField) {
            $fieldHandle = $fieldLayoutField->field->handle;
            if ($fields === null || in_array($fieldHandle, $fields)) {
              $field[$fieldHandle] = $entry->getFieldValue($fieldHandle);
            }
        }

        return $field;
    }