lithium\data\source\Database::_fieldsReturn PHP Method

    protected function _fieldsReturn($type, $context, $fields, $schema)
    {
        if ($type === 'create' || $type === 'update') {
            $data = $context->data();
            if (isset($data['data']) && is_array($data['data']) && count($data) === 1) {
                $data = $data['data'];
            }
            if ($fields && is_array($fields) && is_int(key($fields))) {
                $data = array_intersect_key($data, array_combine($fields, $fields));
            }
            $method = "_{$type}Fields";
            return $this->{$method}($data, $schema, $context);
        }
        return empty($fields) ? '*' : join(', ', $fields);
    }