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/Protocol/Text/TextResponseReader.php

@@ -0,0 +1,113 @@
+<?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\Protocol\Text;
+
+use Predis\CommunicationException;
+use Predis\Connection\ComposableConnectionInterface;
+use Predis\Protocol\ProtocolException;
+use Predis\Protocol\ResponseHandlerInterface;
+use Predis\Protocol\ResponseReaderInterface;
+
+/**
+ * Implements a pluggable response reader using the standard wire protocol
+ * defined by Redis.
+ *
+ * @link http://redis.io/topics/protocol
+ * @author Daniele Alessandri <suppakilla@gmail.com>
+ */
+class TextResponseReader implements ResponseReaderInterface
+{
+    private $handlers;
+
+    /**
+     *
+     */
+    public function __construct()
+    {
+        $this->handlers = $this->getDefaultHandlers();
+    }
+
+    /**
+     * Returns the default set of response handlers for all the type of replies
+     * that can be returned by Redis.
+     */
+    private function getDefaultHandlers()
+    {
+        return array(
+            TextProtocol::PREFIX_STATUS     => new ResponseStatusHandler(),
+            TextProtocol::PREFIX_ERROR      => new ResponseErrorHandler(),
+            TextProtocol::PREFIX_INTEGER    => new ResponseIntegerHandler(),
+            TextProtocol::PREFIX_BULK       => new ResponseBulkHandler(),
+            TextProtocol::PREFIX_MULTI_BULK => new ResponseMultiBulkHandler(),
+        );
+    }
+
+    /**
+     * Sets a response handler for a certain prefix that identifies a type of
+     * reply that can be returned by Redis.
+     *
+     * @param string                   $prefix  Identifier for a type of reply.
+     * @param ResponseHandlerInterface $handler Response handler for the reply.
+     */
+    public function setHandler($prefix, ResponseHandlerInterface $handler)
+    {
+        $this->handlers[$prefix] = $handler;
+    }
+
+    /**
+     * Returns the response handler associated to a certain type of reply that
+     * can be returned by Redis.
+     *
+     * @param  string                   $prefix Identifier for a type of reply.
+     * @return ResponseHandlerInterface
+     */
+    public function getHandler($prefix)
+    {
+        if (isset($this->handlers[$prefix])) {
+            return $this->handlers[$prefix];
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function read(ComposableConnectionInterface $connection)
+    {
+        $header = $connection->readLine();
+
+        if ($header === '') {
+            $this->protocolError($connection, 'Unexpected empty header');
+        }
+
+        $prefix = $header[0];
+
+        if (!isset($this->handlers[$prefix])) {
+            $this->protocolError($connection, "Unknown prefix: '$prefix'");
+        }
+
+        $handler = $this->handlers[$prefix];
+
+        return $handler->handle($connection, substr($header, 1));
+    }
+
+    /**
+     * Helper method used to handle a protocol error generated while reading a
+     * reply from a connection to Redis.
+     *
+     * @param ComposableConnectionInterface $connection Connection to Redis that generated the error.
+     * @param string                        $message    Error message.
+     */
+    private function protocolError(ComposableConnectionInterface $connection, $message)
+    {
+        CommunicationException::handle(new ProtocolException($connection, $message));
+    }
+}