Credis

Credis is a simple, no-nonsense interface to the Redis key-value store for modest developers. Due to the way it is implemented, it is flexible and tolerant of changes to the Redis protocol.

This project was forked from one of the many redisent forks.

Getting to work

If you're at all familiar with the Redis protocol and PHP objects, you've already mastered Credis. All Credis does is map the Redis protocol to a PHP object, abstract away the nitty-gritty, and make the return values PHP compatible.

require 'Credis/Client.php';
$redis = new Credis_Client('localhost');
$redis->set('awesome', 'absolutely');
echo sprintf('Is Credis awesome? %s.\n', $redis->get('awesome'));

You use the exact same command names, and the exact same argument order. How wonderful. How about a more complex example?

$redis->rpush('particles', 'proton');
$redis->rpush('particles', 'electron');
$redis->rpush('particles', 'neutron');
$particles = $redis->lrange('particles', 0, -1);
$particle_count = $redis->llen('particles');
echo "<p>The {$particle_count} particles that make up atoms are:</p>";
echo "<ul>";
foreach ($particles as $particle) {
  echo "<li>{$particle}</li>";
}
echo "</ul>";

Be aware that Redis error responses will be wrapped in a CredisException class and thrown, so do be sure to use proper coding techniques.

Clustering your servers

Credis also includes a way for developers to fully utilize the scalability of Redis with multiple servers and consistent hashing. Using the Credis_Cluster class, you can use Credis the same way, except that keys will be hashed across multiple servers. Here is how to set up a cluster:

require 'Credis/Client.php';
require 'Credis/Cluster.php';

$cluster = new Credis_Cluster(array(
  array('host' => '127.0.0.1', 'port' => 6379),
  array('host' => '127.0.0.1', 'port' => 6380),
));

You can then use Credis the way you normally would, i.e., $cluster->set('key', 'value') or $cluster->lrange('particles', 0, -1). But what about when you need to use commands that are server specific and do not operate on keys? You can use routing, with the CredisCluster::to method. To use routing, you need to assign a server an alias in the constructor of the Redis cluster. Aliases are not required on all servers, just the ones you want to be able to access directly.

$cluster = new Credis_Cluster(array(
  'alpha' => array('host' => '127.0.0.1', 'port' => 6379),
  array('host' => '127.0.0.1', 'port' => 6380),
));

Now there is an alias of the server running on 127.0.0.1:6379 called alpha, and can be interacted with like this:

// get server info
$cluster->to('alpha')->info();

Now you have complete programatic control over your Redis servers.

About

© 2009 Justin Poliey © 2011 Colin Mollenhour