pagecache

pagecache - A fast, open source page level cache for opencart

VERSION

Version 1.0.9

DESCRIPTION

This is part of a collection of code intended to help improve the performance and functionality of opencart. See octurbo.com for more information on the effort.

One of the improvements is this simple, but effective, page level cache for opencart. It includes an admin panel, and an installer that will make two simples changes to your main index.php file.

It has been tested so far only on opencart 1.5.6.X, but should work on all of the 1.5.X versions, perhaps with minor tweaks. This is a new piece of software, so we highly recommend you test it well before using. See the CAVEATS section.

Note that we also provide a page cache for Opencart 2.x. See our v2pagecache repo if you're running Opencart version 2.

Requirements

Opencart 1.5.X. Has been tested on 1.5.6.X
PHP 5.4 is STRONGLY recommended
- It will run on PHP5.3, however:
  - PHP5.3.x does not have http_response_code(), so we'll cache things that probably shouldn't be cached, like 5XX errors and "404 Not Found". We looked at ways around this, and there's not anything elegant. It's too bad that opencart made the $headers array within system/library/response.php a private property.
  - Worse, when the cached pages are served, they will have a "200 OK" status. That will result in, for example, Soft 404's
  - There is a little hack that will fix the two problems above. It involves a small change to a core file, so I did not want to incorporate it into this extension. You can see it at the bottom of this github issue.

Installation

Copy all of the files in the upload directory into your main opencart installation
Log into the admin panel of your store
Navigate to the Extensions > Modules tab
You should see the module listed there as "Page Cache"
Click the Install link
There should now be a new link next to "Page Cache" labeled "Edit". Click That link.
Make sure you have a backup copy of your main index.php first, then...
- Click the Enable Cache button
- If the Enable Cache button returns an error, you may need to make the changes to your index.php file manually. See the Manual Installation section.
The cache should now be working

Manual Installation

This extension has to make changes to your main index.php before it will work. There is an "Enable Cache" button in the extension's admin page that can make those changes. However, in some environments, this button may not be able to do that, due to file permissions, a customized installation of opencart, etc. If that's the case, you'll have to make the changes to the index.php manually.

NOTE: THESE MANUAL INSTALLATION INSTRUCTIONS ARE ONLY FOR PEOPLE HAVING ISSUES WITH THE "ENABLE CACHE" BUTTON WITHIN THE PAGECACHE ADMIN PANEL.

There's two changes that need to be made.

At the top of your main index.php file, find this section of code:

    if (file_exists('config.php')) {
        require_once('config.php');
    }

Then, add these 6 lines, exactly as shown below, just after the section of code above:

require_once(DIR_SYSTEM . 'library/pagecache.php');             //PAGECACHE
$pagecache = new PageCache();                                   //PAGECACHE
if ($pagecache->ServeFromCache()) {                             //PAGECACHE
    // exit here if we served this page from the cache          //PAGECACHE
    return;                                                     //PAGECACHE
}                                                               //PAGECACHE

2. At the bottom of your main index.php, find this section of code:

    // Output
    $response->output();

Then, add these 3 lines of code, just after the section of code above:

if ($pagecache->OkToCache()) {                                  //PAGECACHE
    $pagecache->CachePage($response);                           //PAGECACHE
}                                                               //PAGECACHE

OVERVIEW

Very early in opencart's main index.php file, the following lines of code have been added:

require_once(DIR_SYSTEM . 'library/pagecache.php');             //PAGECACHE
$pagecache = new PageCache();                                   //PAGECACHE
if ($pagecache->ServeFromCache()) {                             //PAGECACHE
    // exit here if we served this page from the cache          //PAGECACHE
    return;                                                     //PAGECACHE
}                                                               //PAGECACHE

This section of code looks to see if there's a previously cached file for the url that's currently being requested. If there is, and it's not expired, the request is served from the cache. Because this is very early in the index.php file, and because it exits if served from the cache (via the return() call), it skips over almost all of the processing that opencart normally does. No database calls, etc..so it's very fast.

Later, towards the end of the index.php, the following lines of code have been added. This is very near the end of the file, after whatever page was requested has already been generated by opencart, and served to the end user.

if ($pagecache->OkToCache()) {                                  //PAGECACHE
    $pagecache->CachePage($response);                           //PAGECACHE
}                                                               //PAGECACHE

Here, we're seeing if we should take the page that opencart just generated and cache it. This does add a small amount of overhead in writing out the content twice (once to the browser, and once to the cache file). That is, however, the only notable overhead added, and it's quite minimal.

ADMIN PANEL

This extension includes an easy to use admin panel that allows you to:

Enable and disable the cache
Purge cached files (either all of them, or just the expired ones)
See statistics on the number of cached files, and disk space used, for both currently valid, as well as expired cache files
View, but not change, the settings (you have to manually edit system/library/pagecache.php to change settings).

Here's a screenshot of the admin panel: Pagecache Admin Panel

SETTINGS

In order to keep this page cache lightweight, we do not store settings in the opencart database like a normal opencart extension would. This allows a cached page to be served with almost no opencart code running, and no database calls at all. Therefore, to make changes to settings, you have to hand edit the pagecache.php file. Here's the settings you can safely change:

// These are all near the top of the pagecache.php file  
private $expire='14400'   ; // expire time, in seconds 14400 = 4 hours
private $lang='en'        ; // default language for site
private $currency='USD'   ; // default currency for site

private $addcomment = true; // set to true to add a comment to the bottom
                            // of cached html pages with info+expire time
                            // only works where headers_list() works

private $wrapcomment=true ; // if this is set to true (and $addcoment is
                            // also set to true), we will use a comment
                            // that most html minifiers won't remove, like:
                            // <!--[if IE]><!--comment--><![endif]-->

private $end_flush=false;   // set to true to do an ob_end_flush() before
                            // serving a cached page. Slightly faster
                            // "first byte received" times, but it creates
                            // issues in some environments, hence, it's off
                            // by default

// If using a 3rd party theme that serves different html to 
// mobile/tablet/desktop, you can enable "cachebydevice"
// For the standard opencart theme, use false
// For journal theme, use 'mobiledetect';
// For Opencart Mobile Framework, use 'categorizr'
// For Omtex Mobile Framework, use 'categorizr'
//
// make sure only one of the three lines below is uncommented
private $cachebydevice=false;
//private $cachebydevice='mobiledetect';
//private $cachebydevice='categorizr';


private $skip_urls= array(
    '#checkout/#',
    '#product/compare#',
    '#product/captcha#',
    '#contact/captcha#',
    '#register/country#'
);

A new notes on these settings:

$expire : Because it's in the declaration section of the class, your options to set this are limited...you can't, for example, do $expire=242460. Just figure out the number of seconds you want cached pages to exist before they expire. We used 14400, which is 4 hours.
$lang and $currency : We cache pages for different languages and currencies in different files. These two settings control what the default language and/or currency is if we get an http request that does not have the session variable(s) for each respective setting already set.
$addcomment : Set to true if you want the page cache to append an html comment at the end of the stored cache file that notes the url cached and it's expiry time. This can be helpful since you can see it with live pages via your browser's "view source" functionality. Set to false if you don't want this. We only add the comment if headers_list() is available and indicates that the cached resource is an html page. This keeps us from adding an html comment to a cached JSON response, for example.
$wrapcomment : If true, wraps the comment (see above) with <!-[if IE]

Pagecache

Install / Use

README