CacheNesting

A Processwire module that manages nested caches and their dependencies. It enables you to cache multiple parts of a page with varying expiration.

Description

The CacheNesting module uses the Processwire WireCache class to manage nested caches and their varying expirations. For example, you could cache your complete page output which consists of an header, body and footer. The header and footer will almost never expire and can be easily cached. Whereas, the body consists of an article cache which expires when the page is saved, and an RSS feed which should expire every 6 hours. Since you cannot say which cache will expire next, with WireCache alone it is not possible to create a cache of the whole page which expires whenever a nested cache does.

The CacheNesting module stores dependencies for each cache, so if any of its dependencies expires the dependent cache will be recreated as well.

How To Use

In your template files, call CacheNesting::getCache to receive the cached data and CacheNesting::createCache to store data to cache.

Example

The following code shows the usecase of a page which consists of the data of its body field and its dataThatChangesHourly field. The body's cache should expire whenever the page is saved. However, the field dataThatChangesHourly expires (as the name suggests) hourly. The cache of the complete page depends on the caches of the two fields.

<?php
    $html = CacheNesting::getCache("completePage");

    if (!$html) {
        $body = CacheNesting::getCache("body");
        if (!$body)
            $body = $page->body;
        $shortDated = CacheNesting::getCache("shortDated");
        if (!$shortDated)
            $shortDated = $page->dataThatChangesHourly;

        $html = $body . $shortDated;

        CacheNesting::createCache("body", $body, "id=$page->id");
        CacheNesting::createCache("shortDated", $shortDated, 3600);
        CacheNesting::createCache("completePage", $html, null, array("body", "shortDated"));
    }
    echo $html;

Syntax

Get Cache

Use getCache to get the cache (just the same as with WireCache).

CacheNesting::getCache($cacheName)

Arguments

• $cacheName (string): The name of the cache, e.g. "body".

Return

• Returns the cached content, or null if cache is expired or not available.

Save Cache

Use createCache to store data to the cache.

CacheNesting::createCache($cacheName, $cacheData, $cacheExpire = null, $dependencies = array())

Arguments

• $cacheName (string): The name of the cache, e.g. "body".
• $cacheData (string, Array of non-object values, PageArray): Data to be cached.
• optional: $cacheExpire (int, WireCache constant, string, null): Expiration of the cache as specified by WireCache::save:
  • Lifetime of this cache, in seconds, OR one of the following:
    • Specify one of the WireCache::expire* constants.
    • Specify the future date you want it to expire (as unix timestamp or any strtotime() compatible date format)
    • Provide a Page object to expire when any page using that template is saved.
    • Specify WireCache::expireNever to prevent expiration.
    • Specify WireCache::expireSave to expire when any page or template is saved.
    • Specify selector string matching pages that–when saved–expire the cache.
• optional: $dependencies (Array): Array of dependency cache names, e.g. array("dep1", "dep2").