Slightly Better Caching: The Suite

[code] /** * Update/serve a cached file * * @access public * @return void */

function _display_cache(&$CFG, &$RTR)
{
    // Start session
    session_start();

// For validation messages, you want to bypass a cached form

    if ($_SERVER['REQUEST_METHOD'] != 'GET') {
        return FALSE;
    }

// Cache URI's built with Centralzed Cache URI //---------------------------------------------

    $cacheuri = $this->get_cache_URI();
    $uri = $cacheuri['uri'];
    $cache_path = $cacheuri['path'];
    
    $filepath = $cache_path.md5($uri);

    if ( ! @file_exists($filepath))
    {
        return FALSE;
    }

    if ( ! $fp = @fopen($filepath, 'rb'))
    {
        return FALSE;
    }
        
    flock($fp, LOCK_SH);
    
    $cache = '';
    if (filesize($filepath) > 0)
    {
        $cache = fread($fp, filesize($filepath));
    }

    flock($fp, LOCK_UN);
    fclose($fp);

// Quickly bypass the cache so no one sees '{cached::name}' in their pages, // or so that a user will always bypass a 'logged out' cache.

    $token = strpos($cache,'{cached::');
    if ( FALSE !== ($data = $this->_get_from_session($CFG->item('cache_data_source'))) && is_array($data))
    {
        if ($token === FALSE)
        {
            return FALSE;
        }
    } elseif ($token !== FALSE)
    {
        return FALSE;
    }

// Okay, so they must be returning as the same status -- back to cache...

    /*
     * Seperate headers from content.
     * This is used to output cached headers. <josh@surber.us>
     */
    list($headers, $cache) = explode("\n\n", $cache, 2);

    /*
     * Seperate each header, looking for timestamp
     * The others are output as-is. <josh@surber.us>
     */
    $headers = explode("\n", $headers);
    foreach ($headers as $header) {
        if (FALSE === strpos($header, 'X-CI-timestamp')) {
            $this->set_header($header);
        } else {
            $timestamp = substr($header, 16);
    // Has the file expired? If so we'll delete it.
            if (time() >= trim($timestamp))
            {         
                @unlink&#40;$filepath&#41;;
                log_message('debug', "Cache file has expired. File deleted");
                return FALSE;
            }
        }
    }
    // --------------------------------------------------------------------

    // Display the cache
    $this->_display($cache);
    log_message('debug', "Cache file is current. Sending it to browser.");        
    log_message('debug', "Cache for ".$uri." loaded from ".$filepath);
    return TRUE;
}

[/code]