public function get_group() {
        static $group = null;

        if($_COOKIE['use_mobile_cache'] == 'false') {
        $group = null;
        } elseif($_COOKIE['use_mobile_cache'] == 'true') {
        $group = 'use_mobile_cache';
        } else {
        if ($group === null) {
            if ($this->do_get_group()) {
                foreach ($this->_groups as $config_group => $config) {
                    if (isset($config['enabled']) && $config['enabled'] && isset($config[$this->_compare_key])) {
                        foreach ((array) $config[$this->_compare_key] as $group_compare_value) {
                            if ($group_compare_value && $this->group_verifier($group_compare_value)) {
                                $group = $config_group;
                                return $group;
                            }
                        }
                    }
                }
            }

            $group = false;
        }
        }

        return $group;
    }