Cake\Routing\Route\Route::_persistParams PHP Method

    protected function _persistParams(array $url, array $params)
    {
        foreach ($this->options['persist'] as $persistKey) {
            if (array_key_exists($persistKey, $params) && !isset($url[$persistKey])) {
                $url[$persistKey] = $params[$persistKey];
            }
        }
        return $url;
    }