Retwis ported to modern Redis data types.

The example (and related documentation at redis.io) was not updated for
5 years. Redis had no sorted sets and hashes when the original code was
written (!). An update was really needed.

We also use a modern PHP client now: Predis. A copy is shipped within
this repository to make life easier to newcomers trying Redis for the
first time via this example.

Predis/PubSub/PubSubContext.php

@@ -0,0 +1,141 @@
+<?php
+
+/*
+ * This file is part of the Predis package.
+ *
+ * (c) Daniele Alessandri <suppakilla@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Predis\PubSub;
+
+use Predis\ClientException;
+use Predis\ClientInterface;
+use Predis\Command\AbstractCommand as Command;
+use Predis\NotSupportedException;
+use Predis\Connection\AggregatedConnectionInterface;
+
+/**
+ * Client-side abstraction of a Publish / Subscribe context.
+ *
+ * @author Daniele Alessandri <suppakilla@gmail.com>
+ */
+class PubSubContext extends AbstractPubSubContext
+{
+    private $client;
+    private $options;
+
+    /**
+     * @param ClientInterface $client  Client instance used by the context.
+     * @param array           $options Options for the context initialization.
+     */
+    public function __construct(ClientInterface $client, Array $options = null)
+    {
+        $this->checkCapabilities($client);
+        $this->options = $options ?: array();
+        $this->client = $client;
+
+        $this->genericSubscribeInit('subscribe');
+        $this->genericSubscribeInit('psubscribe');
+    }
+
+    /**
+     * Returns the underlying client instance used by the pub/sub iterator.
+     *
+     * @return ClientInterface
+     */
+    public function getClient()
+    {
+        return $this->client;
+    }
+
+    /**
+     * Checks if the passed client instance satisfies the required conditions
+     * needed to initialize a Publish / Subscribe context.
+     *
+     * @param ClientInterface $client Client instance used by the context.
+     */
+    private function checkCapabilities(ClientInterface $client)
+    {
+        if ($client->getConnection() instanceof AggregatedConnectionInterface) {
+            throw new NotSupportedException('Cannot initialize a PUB/SUB context when using aggregated connections');
+        }
+
+        $commands = array('publish', 'subscribe', 'unsubscribe', 'psubscribe', 'punsubscribe');
+
+        if ($client->getProfile()->supportsCommands($commands) === false) {
+            throw new NotSupportedException('The current profile does not support PUB/SUB related commands');
+        }
+    }
+
+    /**
+     * This method shares the logic to handle both SUBSCRIBE and PSUBSCRIBE.
+     *
+     * @param string $subscribeAction Type of subscription.
+     */
+    private function genericSubscribeInit($subscribeAction)
+    {
+        if (isset($this->options[$subscribeAction])) {
+            $this->$subscribeAction($this->options[$subscribeAction]);
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function writeCommand($method, $arguments)
+    {
+        $arguments = Command::normalizeArguments($arguments);
+        $command = $this->client->createCommand($method, $arguments);
+        $this->client->getConnection()->writeCommand($command);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function disconnect()
+    {
+        $this->client->disconnect();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function getValue()
+    {
+        $response = $this->client->getConnection()->read();
+
+        switch ($response[0]) {
+            case self::SUBSCRIBE:
+            case self::UNSUBSCRIBE:
+            case self::PSUBSCRIBE:
+            case self::PUNSUBSCRIBE:
+                if ($response[2] === 0) {
+                    $this->invalidate();
+                }
+                // The missing break here is intentional as we must process
+                // subscriptions and unsubscriptions as standard messages.
+
+            case self::MESSAGE:
+                return (object) array(
+                    'kind'    => $response[0],
+                    'channel' => $response[1],
+                    'payload' => $response[2],
+                );
+
+            case self::PMESSAGE:
+                return (object) array(
+                    'kind'    => $response[0],
+                    'pattern' => $response[1],
+                    'channel' => $response[2],
+                    'payload' => $response[3],
+                );
+
+            default:
+                $message = "Received an unknown message type {$response[0]} inside of a pubsub context";
+                throw new ClientException($message);
+        }
+    }
+}