yf_output_cache class

    public function refresh($event = '', $params = [])
    {
    }

    public function __call($name, $args)
    {
        return main()->extend_call($this, $name, $args);
    }

    public function _cache_refresh_all()
    {
    }

    public function _check_if_need_to_cache()
    {
        // Fast implementation of disabling output caching for the current page
        if (conf('no_output_cache')) {
            $this->NO_NEED_TO_CACHE = true;
            return false;
        }
        if (main()->NO_GRAPHICS && ! conf('output_cache_force')) {
            $this->NO_NEED_TO_CACHE = true;
            return false;
        }
        if (($_SESSION['user_group'] ?? null) > 1 || ($_COOKIE['member_id'] ?? null)) {
            $this->NO_NEED_TO_CACHE = true;
            return false;
        }
        // Special for the 'share on facebook' feature
        if (false !== strpos(($_SERVER['HTTP_USER_AGENT'] ?? ''), 'facebookexternalhit')) {
            $this->NO_NEED_TO_CACHE = true;
            return false;
        }
        // Check 'white' list first
        $w = $this->WHITE_LIST_PATTERN;
        if ( ! empty($w)) {
            // Array like: 'search' => array(), 'static_pages' => array('show')
            if (is_array($w)) {
                if ( ! isset($w[$_GET['object']])) {
                    $this->NO_NEED_TO_CACHE = true;
                    return $this->NO_NEED_TO_CACHE;
                } elseif ( ! empty($w[$_GET['object']]) && ! in_array(($_GET['action'] ?? null), (array) $w[$_GET['object']])) {
                    $this->NO_NEED_TO_CACHE = true;
                    return $this->NO_NEED_TO_CACHE;
                }
            } else {
                if ( ! preg_match('/' . $w . '/i', $_SERVER['QUERY_STRING'])) {
                    $this->NO_NEED_TO_CACHE = true;
                    return $this->NO_NEED_TO_CACHE;
                }
            }
            return false;
        }
        // Try to search current query string in the stop list
        foreach ((array) $this->_OC_STOP_LIST as $pattern) {
            if (preg_match('/' . $pattern . '/i', $_SERVER['QUERY_STRING'])) {
                $this->NO_NEED_TO_CACHE = true;
                return $this->NO_NEED_TO_CACHE;
            }
        }
        return false; // Default return value
    }

    public function _clean_by_hashes($hashes = [])
    {
    }

    public function _clean_by_params($params = [])
    {
    }

    public function _clean_by_sql($sql = '')
    {
    }

    public function _exec_trigger($params = [])
    {
    }

    public function _get_page_cache_name()
    {
        if ( ! isset($this->_cur_cache_name)) {
            $this->_cur_cache_name = md5(
                ($_SERVER['HTTP_HOST'] ?? null)
                . '/' . ($_SERVER['SCRIPT_NAME'] ?? null)
                . '?' . ($_SERVER['QUERY_STRING'] ?? null)
                . '---' . conf('language')
                . '---' . (int) conf('SITE_ID')
                . '---' . (($_SESSION['user_group'] ?? null) <= 1 ? 'guest' : 'member')
            );
        }
        return $this->_cur_cache_name;
    }

    public function _init($params = [])
    {
        // Assign group_id = 1 for guests
        if (empty($_SESSION['user_group'])) {
            $_SESSION['user_group'] = 1;
        }
        $this->OUTPUT_CACHING = main()->OUTPUT_CACHING;

        if (($_SESSION['user_group'] ?? null) > 1 || ($_COOKIE['member_id'] ?? null)) {
            main()->OUTPUT_CACHING = false;
            $this->OUTPUT_CACHING = false;
        }
        // Ability to handle output cache through http query
        if ($this->OUTPUT_CACHING && $this->CACHE_CONTROL_FROM_URL) {
            // Display current page without as it is without cache
            if (isset($_GET['no_cache']) || false !== strpos(($_SERVER['REQUEST_URI'] ?? ''), '?no_cache')) {
                conf('no_output_cache', true);
            }
            if (isset($_GET['refresh_cache']) || false !== strpos(($_SERVER['REQUEST_URI'] ?? ''), '?refresh_cache')) {
                conf('refresh_output_cache', true);
            }
        }
        parent::_init($params);
    }

    public function _post_filter()
    {
    }

    public function _pre_filter($body = '')
    {
        return $body;
    }

    public function _process_output_cache()
    {
        $this->_check_if_need_to_cache();
        if ( ! $this->OUTPUT_CACHING || ($_SERVER['REQUEST_METHOD'] ?? null) != 'GET' || MAIN_TYPE_ADMIN || $this->NO_NEED_TO_CACHE) {
            return false;
        }
        if (DEBUG_MODE) {
            $time_start = microtime(true);
        }
        $cache_key = $this->CACHE_NS . $this->_get_page_cache_name();
    }

    public function _put_page_to_output_cache($body = [])
    {
        $this->_check_if_need_to_cache();
    }

    public function _send_http_headers($cache_last_modified_time = 0)
    {
        // Send correct headers
        header('Content-Type: text/html; charset=' . conf('charset'), 1);
        header('Content-language: ' . conf('language'), 1);
        header('Expires: ' . gmdate('D, d M Y H:i:s', $cache_last_modified_time + 600/*$this->OUTPUT_CACHE_TTL*/) . ' GMT', 1);
        header('Cache-Control: ', 1);
        header('Pragma: ', 1);
        // Set default values:
        $date = gmdate('D, d M Y H:i:s', $cache_last_modified_time) . ' GMT';
        $etag = '' . md5($date) . '';
        // Check http headers:
        $modified_since = isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) ? ($_SERVER['HTTP_IF_MODIFIED_SINCE'] ?? null) == $date : null;
        if ( ! empty($_SERVER['HTTP_IF_MODIFIED_SINCE']) && ($timestamp = strtotime(($_SERVER['HTTP_IF_MODIFIED_SINCE'] ?? ''))) > 0) {
            $modified_since = $cache_last_modified_time <= $timestamp;
        } else {
            $modified_since = null;
        }
        $none_match = ! empty($_SERVER['HTTP_IF_NONE_MATCH']) ? ($_SERVER['HTTP_IF_NONE_MATCH'] ?? null) == $etag : null;
        // The type checking here is very important, be careful when changing entries.
        if (($modified_since !== null || $none_match !== null) && $modified_since !== false && $none_match !== false) {
            header('HTTP/1.0 304 Not Modified');
            exit();
        }
        // Send appropriate response:
        header('Last-Modified: ' . $date, 1);
        header('ETag: ' . $etag, 1);
    }