Web Page Caching

CodeIgniter lets you cache your pages in order to achieve maximum performance.

Although CodeIgniter is quite fast, the amount of dynamic information you display in your pages will correlate directly to the server resources, memory, and processing cycles utilized, which affect your page load speeds. By caching your pages, since they are saved in their fully rendered state, you can achieve performance much closer to that of static web pages.

How Does Caching Work?

Caching can be enabled on a per-page basis, and you can set the length of time that a page should remain cached before being refreshed.

Note

Per-page means per URI. Since v4.5.0, the HTTP method of the request is also taken into account. This means that the same URI will be cached separately if the HTTP method is different.

When a page is loaded for the first time, the page will be cached using the currently configured cache engine. On subsequent page loads, the cache will be retrieved and sent to the requesting user’s browser.

If it has expired, it will be deleted and refreshed before being sent to the browser.

Note

The Benchmark tag is not cached so you can still view your page load speed when caching is enabled.

Configuring Caching

Setting Cache Engine

Before using Web Page Caching, you must set the cache engine up by editing app/Config/Cache.php. See Configuring the Cache for details.

Setting $cacheQueryString

You can set whether or not to include the query string when generating the cache with Config\Cache::$cacheQueryString.

Valid options are:

  • false: (default) Disabled. The query string is not taken into account; the same cache is returned for requests with the same URI path but different query strings.

  • true: Enabled, take all query parameters into account. Be aware that this may result in numerous cache generated for the same page over and over again.

  • array: Enabled, but only take into account the specified list of query parameters. E.g., ['q', 'page'].

Setting $cacheStatusCodes

New in version 4.7.0.

You can control which HTTP response status codes are allowed to be cached with Config\Cache::$cacheStatusCodes.

Valid options are:

  • []: (default) Cache all HTTP status codes. This maintains backward compatibility but may cache temporary error pages.

  • [200]: (Recommended) Only cache successful responses. This prevents caching of error pages (404, 500, etc.) that should be temporary.

  • array of status codes: Cache only specific status codes. For example:

    • [200, 404]: Cache successful responses and not found pages.

    • [200, 404, 410]: Cache successful responses and specific error codes.

    • [200, 201, 202, 203, 204]: All 2xx successful responses.

Warning

Using an empty array [] may cache temporary error pages (404, 500, etc). For production applications, consider restricting this to [200] to avoid caching errors that should be temporary. For example, a cached 404 page would remain cached even after the resource is created, until the cache expires.

Note

Regardless of this setting, DownloadResponse and RedirectResponse instances are never cached by the PageCache filter.

Enabling Caching

To enable caching, put the following tag in any of your controller methods:

<?php

$this->cachePage($n);

Where $n is the number of seconds you wish the page to remain cached between refreshes.

The above tag can go anywhere within a method. It is not affected by the order that it appears, so place it wherever it seems most logical to you. Once the tag is in place, your pages will begin being cached.

Important

If you change configuration options that might affect your output, you have to manually delete your cache.

Deleting Caches

If you no longer wish to cache a page you can remove the caching tag and it will no longer be refreshed when it expires.

Note

Removing the tag will not delete the cache immediately. It will have to expire normally.