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Germania KG · CacheCallable

Callable convenience wrapper around PSR-6 Cache Item Pools: Seamlessly creates, returns, and stores your data.

Caching business is pretty much always similar and can be outlined like this:

1. Is caching enabled at all? If not, delete any according older entry first.
   Create and return fresh content anyway, ending up here.
2. Does a given item exist? If so, return item content;
   Otherwise, create, store and return content.

The CacheCallable class reduces these steps to a handy and customizable Callable.

Installation with Composer

Example

Although this example uses phpfastcache, you should be able to pass in any Cache Item Pool. Use your favourite PSR-3 Logger; this example will use the well-known Monolog.

A word on cache keys

According to the PSR-6 specs, cache keys should be limited to A-Z, a-z, 0-9, _, and . to ensure maximum compatibilty. So if you pass in a PSR-6 Adapter from Symfony Cache component, class CacheCallable internally converts the given keys to a MD5 representation.

In case you'd like to provide a custom cache key creation, you may use the setCacheKeyCreator method whoch accepts any callable:

PHP-FIG: PSR-6: Caching Interface

Implementing libraries MUST support keys consisting of the characters A-Z, a-z, 0-9, _, and . in any order in UTF-8 encoding and a length of up to 64 characters. Implementing libraries MAY support additional characters and encodings or longer lengths, but must support at least that minimum.

Symfony docs: “Cache Item Keys and Values”

The key of a cache item […] should only contain letters (A-Z, a-z), numbers (0-9) and the _ and . symbols.

The Cache lifetime

Think of a webpage that turns out to be not cached during script runtime — after we set up the Cache wrapper. For this reason, the Cache wrapper constructor also accepts a LifeTimeInterface implementation with a getValue method:

The LifeTime class is a simple implementation of this interface. It additionally enables you to change the lifetime value during runtime. Since we passed it to our Cache constructor by reference, the Cache wrapper can decide after content creation wether to cache or not.

Create a Lifetime object

Usage with CacheCallable

Your Logger will now output something like this:

How to change lifetime during script runtime

After instantation, you may use the setValue method:

The LifeTime class is a simple implementation of this interface. It additionally enables you to change the lifetime value during runtime. Since we passed it to our Cache constructor by reference, the Cache wrapper can decide after content creation wether to cache or not.

Create a Lifetime object:

Set time value after instantation

Usage with CacheCallable

Your Logger will now output something like this:

How to override content creation

If you prefer singleton services, you may invoke the CacheCallable with a custom content creator parameter to override the default one:

Issues

The PSR-6 Caching Interface mock in CacheCallableTest could need an overhaul. Discuss on #issue 3

Development

Unit tests

Either copy phpunit.xml.dist to phpunit.xml and adapt to your needs, or leave as is. Run PhpUnit test or composer scripts like this:

Useful Links

• PSR-6: Caching Interface
• PSR-6 CacheItemPoolInterface
• PSR-6 CacheItemInterface