serialize json view cakephp3

gistfile1.txt

    protected function _dataToSerialize($serialize = true)
    {
        if ($serialize === true) {
            $data = array_diff_key(
                $this->viewVars,
                array_flip($this->_specialVars)
            );

            if (empty($data)) {
                return null;
            }

            return $data;
        }

        if (is_array($serialize)) {
            //added
            $j = 1;
            $data = [];
            foreach ($serialize as $alias => $key) {
                if (is_numeric($alias)) {
                    $alias = $key;
                }
                if (array_key_exists($key, $this->viewVars)) {
                    $data[$alias] = $this->viewVars[$key];
                    //added
                    $data[$alias][$key]['recid'] = $j++;
                }
            }

            return !empty($data) ? $data : null;
        }

        return isset($this->viewVars[$serialize]) ? $this->viewVars[$serialize] : null;
    }