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/ConnectionFactoryInterface.php

@@ -0,0 +1,53 @@
+<?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;
+
+/**
+ * Interface that must be implemented by classes that provide their own mechanism
+ * to create and initialize new instances of Predis\Connection\SingleConnectionInterface.
+ *
+ * @author Daniele Alessandri <suppakilla@gmail.com>
+ */
+interface ConnectionFactoryInterface
+{
+    /**
+     * Defines or overrides the connection class identified by a scheme prefix.
+     *
+     * @param string $scheme      URI scheme identifying the connection class.
+     * @param mixed  $initializer FQN of a connection class or a callable object for lazy initialization.
+     */
+    public function define($scheme, $initializer);
+
+    /**
+     * Undefines the connection identified by a scheme prefix.
+     *
+     * @param string $scheme Parameters for the connection.
+     */
+    public function undefine($scheme);
+
+    /**
+     * Creates a new connection object.
+     *
+     * @param  mixed                     $parameters Parameters for the connection.
+     * @return SingleConnectionInterface
+     */
+    public function create($parameters);
+
+    /**
+     * Prepares an aggregation of connection objects.
+     *
+     * @param  AggregatedConnectionInterface $cluster    Instance of an aggregated connection class.
+     * @param  array                         $parameters List of parameters for each connection object.
+     * @return AggregatedConnectionInterface
+     */
+    public function createAggregated(AggregatedConnectionInterface $cluster, Array $parameters);
+}