Cache layer

Cache layer for PHP applications capable of being used standalone or with the Chain of Responsability pattern.

1. Installation

The recommended way to install this package is through Composer. Run the following command to install it:

php composer.phar require nilportugues/cache

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2. Features

• One cache class, many adapters.
• All cache adapters can be used as standalone cache classes.
• Opt-in to be used as a chain of caches.
• Implementation normalizes all mechanisms and behaviours.
• Configuration files for all adapters in vanilla PHP and Symfony2 format provided in configand migrations directories.
• High quality, 100% tested code.

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3. Drivers Available

The package provides several implementations for a key-value cache.

The most sensitive choice is to make use of the Cache based adapters such as Redis and Memcached, which are the most performant and specialized.

Yet sometimes these are not available and other options should be considered, but we got you covered.

Cache based:

• Memcached: MemcachedAdapter (php5-memcached)
• Redis: RedisAdapter (php5-redis), PredisAdapter (Predis)

Full-text based:

• SphinxQL: SphinxAdapter
• ElasticSearch: ElasticSearchAdapter

System based:

• Memory: InMemoryAdapter
• FileSystem: FileSystemAdapter

Database based:

• MySQL: MySqlAdapter
• PostgreSql: PostgreSqlAdapter
• Sqlite: SqliteAdapter

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4. Cache and CacheAdapter Interfaces

These are all the public methods available for the Cache and all of its available adapters:

• get($key): Get a value identified by $key.
• set($key, $value, $ttl = 0): Set a value identified by $key and with an optional $ttl.
• defaultTtl($ttl): Allows to set a default ttl value if none is provided for set()
• delete($key): Delete a value identified by $key.
• isAvailable(): Checks the availability of the cache service.
• isHit(): Check if value was found in the cache or not.
• clear(): Clears all expired values from cache.
• drop(): Clears all values from the cache.

4.1 - CacheAdapter

Allows all of the public methods defined in Cache Interface.

Each CacheAdapter will have a custom constructor method due to its needs, but last parameter is always a chainable value, being another CacheAdapter.

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5. Example

The more cache levels the slower the cache system will be, so leverage the 
cache to your needs. 
Maybe you don't need a fallback mechanism at all! This is just an example.

1st level cache Redis (PredisAdapter) is our main cache, in a dedicated server.

2nd level cache Memcached (MemcachedAdapter) as fallback mechanism, available in the same machine as our PHP script.

Application cache InMemoryAdapter, used to avoid hiting the external caches on repeated operations and is shared by all cache layers. This comes enabled by default so you don't need to worry at all.

5.1. Configuration

Using a Service Container, such as an array returning the services or a more popular solution such as Symfony's Service Container, build the caches.

For this example, we'll be building two caches, user_cache and image_cache. Both use Predis as first level cache and a fallback to Memcached if Predis cannot establish a connection during runtime.

<?php
include_once realpath(dirname(__FILE__)).'/vendor/autoload.php';

use NilPortugues\Cache\Adapter\MemcachedAdapter;
use NilPortugues\Cache\Adapter\PredisAdapter;
use NilPortugues\Cache\Cache;

$parameters = include_once realpath(dirname(__FILE__)).'/cache_parameters.php';

$cache = new PredisAdapter(
    $parameters['redis'],
    //here we're chaining the $memcachedAdapter
    new MemcachedAdapter(
        $parameters['memcached']['persistent_id'],
        $parameters['memcached']['connections']
    );
);

return [
    'user_cache' => new Cache($cache, 'user', 60*5), //5 minutes cache
    'image_cache' => new Cache($cache, 'image', 60*60), //1 hour cache
];

5.2. Usage

Now, using a Service Container, we'll get the user_cache to fetch data, or add if it does not exist. This data will be stored in the caches.

For fetching, first it's checked if data is available in memory, if not, it's fetched from the data storage, added to the in memory cache and returned to the user.

$db = $this->serviceContainer->get('database');
$cache = $this->serviceContainer->get('cache');

$userId = 1;
$cacheKey = sprintf("user:id:%s", $userId);

$user = $cache->get($cacheKey);
if(null !== $user) {
  return $user;
}

$user = $db->findById($userId);
$cache->set($cacheKey, $user);

return $user;

And that's pretty much it. Notice how same key is used for the get and set methods.

5.3 Other configurations

5.3.1 ElasticSearch as cache

It is important that you configure your ElasticSearch by appending the following line to the elasticsearch.yml file:

indices.ttl.interval: 1s

Now restart the ElasticSearch daemon.

If you're wondering where the cache index definition is, the creation of index is handled by the adapter on instantiation if it does not already exist.

5.3.2 Sphinx as cache

Configuration provided in the /migrations/sphinx.conf file.

5.3.3 MySQL as cache

Configuration provided in the /migrations/mysql_schema.sql file.

5.3.4 Postgres as cache

Configuration provided in the /migrations/postgresql_schema.sql file.

5.3.5 Sqlite as cache

Configuration provided in the /migrations/sqlite_schema.sqlite file.

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6. Quality

To run the PHPUnit tests at the command line, go to the tests directory and issue phpunit.

This library attempts to comply with PSR-1, PSR-2, and PSR-4. If you notice compliance oversights, please send a patch via pull request.

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7. Author

Nil Portugués Calderó

• contact@nilportugues.com
• http://nilportugues.com

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8. License

The code base is licensed under the MIT license.