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/Connection/AggregatedConnectionInterface.php

@@ -0,0 +1,55 @@
+<?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\Connection;
+
+use Predis\Command\CommandInterface;
+
+/**
+ * Defines a virtual connection composed by multiple connection objects.
+ *
+ * @author Daniele Alessandri <suppakilla@gmail.com>
+ */
+interface AggregatedConnectionInterface extends ConnectionInterface
+{
+    /**
+     * Adds a connection instance to the aggregated connection.
+     *
+     * @param SingleConnectionInterface $connection Instance of a connection.
+     */
+    public function add(SingleConnectionInterface $connection);
+
+    /**
+     * Removes the specified connection instance from the aggregated
+     * connection.
+     *
+     * @param  SingleConnectionInterface $connection Instance of a connection.
+     * @return bool                      Returns true if the connection was in the pool.
+     */
+    public function remove(SingleConnectionInterface $connection);
+
+    /**
+     * Gets the actual connection instance in charge of the specified command.
+     *
+     * @param  CommandInterface          $command Instance of a Redis command.
+     * @return SingleConnectionInterface
+     */
+    public function getConnection(CommandInterface $command);
+
+    /**
+     * Retrieves a connection instance from the aggregated connection
+     * using an alias.
+     *
+     * @param  string                    $connectionId Alias of a connection
+     * @return SingleConnectionInterface
+     */
+    public function getConnectionById($connectionId);
+}