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Flexible and feature-complete PHP client library for Redis

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README.md

Predis

Predis is a flexible and feature-complete PHP (>= 5.3) client library for the Redis key-value store.

The library does not require any additional extension loaded in PHP but it can be optionally paired with the phpiredis C-based extension to lower the overhead of serializing and parsing the Redis protocol. Predis is also available in an asynchronous fashion through the experimental client provided by the Predis\Async library.

For a list of frequently asked questions about Predis see our FAQ. More details are available on the official wiki of the project.

Main features

  • Wide range of Redis versions supported (from 1.2 to 2.6 and unstable) using server profiles.
  • Smart support for redis-cluster (Redis >= 3.0).
  • Client-side sharding via consistent hashing or custom distribution strategies.
  • Support for master / slave replication configurations (write on master, read from slaves).
  • Transparent key prefixing strategy capable of handling any command known that has keys in its arguments.
  • Command pipelining on single and aggregated connections.
  • Abstraction for Redis transactions (Redis >= 2.0) with support for CAS operations (Redis >= 2.2).
  • Abstraction for Lua scripting (Redis >= 2.6) capable of automatically switching between EVAL and EVALSHA.
  • Connections to Redis instances are lazily established upon the first call to a command by the client.
  • Ability to connect to Redis using TCP/IP or UNIX domain sockets with support for persistent connections.
  • Ability to specify alternative connection classes to use different types of network or protocol backends.
  • Flexible system to define and register your own set of commands or server profiles to client instances.

How to use Predis

Predis is available on Packagist for an easy installation using Composer. Composer helps you manage dependencies for your projects and libraries without much hassle which makes it the preferred way to get up and running with new applications. Alternatively, the library is available on our own PEAR channel for a more traditional installation via PEAR. Zip and tar.gz archives are also downloadable from GitHub by browsing the list of tagged releases.

Loading the library

Predis relies on the autoloading features of PHP to load its files when needed and complies with the PSR-0 standard which makes it compatible with most of the major frameworks and libraries. Autoloading in your application is handled automatically when managing the dependencies with Composer, but you can also leverage its own autoloader class if you are going to use it in a project or script without any PSR-0 compliant autoloading facility:

<?php
// prepend a base path if Predis is not present in your "include_path".
require 'Predis/Autoloader.php';

Predis\Autoloader::register();

It is possible to create a single Phar archive from the repository just by launching bin/create-phar.php. The generated Phar archive ships with a stub defining an autoloader function for Predis, so you just need to require the Phar to be able to use the library.

Alternatively it is possible to generate a single PHP file that holds every class, just like older versions of Predis, using bin/create-single-file.php. In this way you can load Predis in your scripts simply by using functions such as require and include, but this practice is not encouraged.

Connecting to Redis

By default Predis uses 127.0.0.1 and 6379 as the default host and port when creating a new client instance without specifying any connection parameter:

$redis = new Predis\Client();
$redis->set('foo', 'bar');
$value = $redis->get('foo');

It is possible to specify the various connection parameters using URI strings or named arrays:

$redis = new Predis\Client('tcp://10.0.0.1:6379');

// is equivalent to:

$redis = new Predis\Client(array(
    'scheme' => 'tcp',
    'host'   => '10.0.0.1',
    'port'   => 6379,
));

Pipelining commands to multiple instances of Redis with client-side sharding

Pipelining helps with performances when there is the need to send many commands to a server in one go. Furthermore, pipelining works transparently even on aggregated connections. To achieve this, Predis supports client-side sharding using consistent-hashing on keys while clustered connections are supported natively by the client class.

$redis = new Predis\Client(array(
    array('host' => '10.0.0.1', 'port' => 6379),
    array('host' => '10.0.0.2', 'port' => 6379)
));

$replies = $redis->pipeline(function ($pipe) {
    for ($i = 0; $i < 1000; $i++) {
        $pipe->set("key:$i", str_pad($i, 4, '0', 0));
        $pipe->get("key:$i");
    }
});

Multiple and customizable connection backends

Predis can optionally use different connection backends to connect to Redis. Two of them leverage the phpiredis C-based extension resulting in a major speed bump especially when dealing with long multibulk replies, namely Predis\Connection\PhpiredisConnection (the socket extension is also required) and Predis\Connection\StreamPhpiredisConnection (it does not require additional extensions since it relies on PHP's native streams). Both of them can connect to Redis using standard TCP/IP connections or UNIX domain sockets:

$client = new Predis\Client('tcp://127.0.0.1', array(
    'connections' => array(
        'tcp'  => 'Predis\Connection\PhpiredisConnection',
        'unix' => 'Predis\Connection\PhpiredisStreamConnection',
    )
));

Developers can also create their own connection backends to add support for new protocols, extend existing ones or provide different implementations. Connection backend classes must implement Predis\Connection\SingleConnectionInterface or extend Predis\Connection\AbstractConnection:

class MyConnectionClass implements Predis\Connection\SingleConnectionInterface
{
    // implementation goes here
}

// Let Predis automatically use your own class to handle connections identified by the tcp scheme.
$client = new Predis\Client('tcp://127.0.0.1', array(
    'connections' => array('tcp' => 'MyConnectionClass')
));

For a more in-depth insight on how to create new connection backends you can look at the actual implementation of the classes contained in the Predis\Connection namespace.

Defining and registering new commands on the client at runtime

Let's suppose Redis just added the support for a brand new feature associated with a new command. If you want to start using the above mentioned new feature right away without messing with Predis source code or waiting for it to find its way into a stable Predis release, then you can start off by creating a new class that matches the command type and its behaviour and then bind it to a client instance at runtime. Actually, it is easier done than said:

class BrandNewRedisCommand extends Predis\Command\AbstractCommand
{
    public function getId()
    {
        return 'NEWCMD';
    }
}

$redis = new Predis\Client();
$redis->getProfile()->defineCommand('newcmd', 'BrandNewRedisCommand');
$redis->newcmd();

Abstraction for handling Lua scripts as plain Redis commands

A scripted command in Predis is an abstraction for Lua scripting with Redis >= 2.6 that allows to use a Lua script as if it was a plain Redis command registered in the server profile being used by the client instance. Internally, scripted commands use EVALSHA to refer to a Lua script by its SHA1 hash in order to save bandwidth, but they are capable of falling back to EVAL when needed:

class ListPushRandomValue extends Predis\Command\ScriptedCommand
{
    public function getKeysCount()
    {
        return 1;
    }

    public function getScript()
    {
        return
<<<LUA
math.randomseed(ARGV[1])
local rnd = tostring(math.random())
redis.call('lpush', KEYS[1], rnd)
return rnd
LUA;
    }
}

$client = new Predis\Client();
$client->getProfile()->defineCommand('lpushrand', 'ListPushRandomValue');

$value = $client->lpushrand('random_values', $seed = mt_rand());

Test suite

ATTENTION: Do not ever run the test suite shipped with Predis against instances of Redis running in production environments or containing data you are interested in!

Predis has a comprehensive test suite covering every aspect of the library. The suite performs integration tests against a running instance of Redis (>= 2.4.0 is required) to verify the correct behaviour of the implementation of each command and automatically skips commands not defined in the selected version of Redis. If you do not have Redis up and running, integration tests can be disabled. By default, the test suite is configured to execute integration tests using the server profile for Redis v2.4 (which is the current stable version of Redis). You can optionally run the suite against a Redis instance built from the unstable branch with the development profile by changing the REDIS_SERVER_VERSION to dev in the phpunit.xml file. More details on testing Predis can be found in the tests README.

Predis uses Travis CI for continuous integration. You can find the results of the test suite and the build history on its project page.

Dependencies

  • PHP >= 5.3.2
  • PHPUnit >= 3.5.0 (needed to run the test suite)

Links

Project

Related

Author

Contributors

License

The code for Predis is distributed under the terms of the MIT license (see LICENSE).

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