Twig cache extension

The missing cache extension for Twig. The extension allows for caching rendered parts of templates using several cache strategies.

Installation

The extension is installable via composer:

{
    "require": {
        "asm89/twig-cache-extension": "~1.0"
    }
}

Quick start

Setup

A minimal setup for adding the extension with the LifeTimeCacheStrategy and doctrine array cache is as following:

<?php

use Doctrine\Common\Cache\ArrayCache;
use Asm89\Twig\CacheExtension\CacheProvider\DoctrineCacheAdapter;
use Asm89\Twig\CacheExtension\CacheStrategy\LifetimeCacheStrategy;
use Asm89\Twig\CacheExtension\Extension as CacheExtension;

$cacheProvider  = new DoctrineCacheAdapter(new ArrayCache());
$cacheStrategy  = new LifetimeCacheStrategy($cacheProvider);
$cacheExtension = new CacheExtension($cacheStrategy);

$twig->addExtension($cacheExtension);

Want to use a PSR-6 cache pool?

Instead of using the default DoctrineCacheAdapter the extension also has a PSR-6 compatible adapter. You need to instantiate one of the cache pool implementations as can be found on: http://php-cache.readthedocs.io/en/latest/

Example: Making use of the ApcuCachePool via the PsrCacheAdapter:

composer require cache/apcu-adapter

<?php

use Asm89\Twig\CacheExtension\CacheProvider\PsrCacheAdapter;
use Asm89\Twig\CacheExtension\CacheStrategy\LifetimeCacheStrategy;
use Asm89\Twig\CacheExtension\Extension as CacheExtension;
use Cache\Adapter\Apcu\ApcuCachePool;

$cacheProvider  = new PsrCacheAdapter(new ApcuCachePool());
$cacheStrategy  = new LifetimeCacheStrategy($cacheProvider);
$cacheExtension = new CacheExtension($cacheStrategy);

$twig->addExtension($cacheExtension);

Usage

To cache a part of a template in Twig surround the code with a cache block. The cache block takes two parameters, first an "annotation" part, second the "value" the cache strategy can work with. Example:

{% cache 'v1/summary' 900 %}
    {# heavy lifting template stuff here, include/render other partials etc #}
{% endcache %}

Cache blocks can be nested:

{% cache 'v1' 900 %}
    {% for item in items %}
        {% cache 'v1' item %}
            {# ... #}
        {% endcache %}
    {% endfor %}
{% endcache %}

The annotation can also be an expression:

{% set version = 42 %}
{% cache 'hello_v' ~ version 900 %}
    Hello {{ name }}!
{% endcache %}

Cache strategies

The extension ships with a few cache strategies out of the box. Setup and usage of all of them is described below.

Lifetime

See the "Quick start" for usage information of the LifetimeCacheStrategy.

Generational

Strategy for generational caching.

In theory the strategy only saves fragments to the cache with infinite lifetime. The key of the strategy lies in the fact that the keys for blocks will change as the value for which the key is generated changes.

For example: entities containing a last update time, would include a timestamp in the key. For an interesting blog post about this type of caching see: http://37signals.com/svn/posts/3113-how-key-based-cache-expiration-works

Blackhole

Strategy for development mode.

In development mode it often not very useful to cache fragments. The blackhole strategy provides an easy way to not cache anything it all. It always generates a new key and does not fetch or save any fragments.

Setup

In order to use the strategy you need to setup a KeyGenerator class that is able to generate a cache key for a given value.

The following naive example always assumes the value is an object with the methods getId() and getUpdatedAt() method. The key then composed from the class name, the id and the updated time of the object:

<?php

use Asm89\Twig\CacheExtension\CacheStrategy\KeyGeneratorInterface;

class MyKeyGenerator implements KeyGeneratorInterface
{
    public function generateKey($value)
    {
        return get_class($value) . '_' . $value->getId() . '_' . $value->getUpdatedAt();
    }

}

Next the GenerationalCacheStrategy needs to be setup with the keygenerator.

<?php

use Asm89\Twig\CacheExtension\CacheStrategy\GenerationalCacheStrategy;
use Asm89\Twig\CacheExtension\Extension as CacheExtension;

$keyGenerator   = new MyKeyGenerator();
$cacheProvider  = /* see Quick start */;
$cacheStrategy  = new GenerationalCacheStrategy($cacheProvider, $keyGenerator, 0 /* = infinite lifetime */);
$cacheExtension = new CacheExtension($cacheStrategy);

$twig->addExtension($cacheExtension);

Usage

The strategy expects an object as value for determining the cache key of the block:

{% cache 'v1/summary' item %}
    {# heavy lifting template stuff here, include/render other partials etc #}
{% endcache %}

Using multiple strategies

Different cache strategies are useful for different usecases. It is possible to mix multiple strategies in an application with the IndexedChainingCacheStrategy. The strategy takes an array of 'name' => $strategy and delegates the caching to the appropriate strategy.

Setup

<?php

use Asm89\Twig\CacheExtension\CacheStrategy\IndexedChainingCacheStrategy;
use Asm89\Twig\CacheExtension\Extension as CacheExtension;

$cacheStrategy  = new IndexedChainingCacheStrategy(array(
    'time' => $lifetimeCacheStrategy,
    'gen'  => $generationalCacheStrategy,
));
$cacheExtension = new CacheExtension($cacheStrategy);

$twig->addExtension($cacheExtension);

Usage

The strategy expects an array with as key the name of the strategy which it needs to delegate to and as value the appropriate value for the delegated strategy.

{# delegate to lifetime strategy #}
{% cache 'v1/summary' {time: 300} %}
    {# heavy lifting template stuff here, include/render other partials etc #}
{% endcache %}

{# delegate to generational strategy #}
{% cache 'v1/summary' {gen: item} %}
    {# heavy lifting template stuff here, include/render other partials etc #}
{% endcache %}

Implementing a cache strategy

Creating separate caches for different access levels, languages or other usecases can be done by implementing a custom cache strategy. In order to do so implement the CacheProviderInterface. It is recommended to use composition and wrap a custom strategy around an existing one.

Authors

Alexander iam.asm89@gmail.com

License

twig-cache-extension is licensed under the MIT License - see the LICENSE file for details