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/TextProtocol.php

@@ -0,0 +1,137 @@
+<?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\ResponseError;
+use Predis\ResponseQueued;
+use Predis\Command\CommandInterface;
+use Predis\Connection\ComposableConnectionInterface;
+use Predis\Iterator\MultiBulkResponseSimple;
+use Predis\Protocol\ProtocolException;
+use Predis\Protocol\ProtocolInterface;
+
+/**
+ * Implements a protocol processor for the standard wire protocol defined by Redis.
+ *
+ * @link http://redis.io/topics/protocol
+ * @author Daniele Alessandri <suppakilla@gmail.com>
+ */
+class TextProtocol implements ProtocolInterface
+{
+    const NEWLINE = "\r\n";
+    const OK      = 'OK';
+    const ERROR   = 'ERR';
+    const QUEUED  = 'QUEUED';
+    const NULL    = 'nil';
+
+    const PREFIX_STATUS     = '+';
+    const PREFIX_ERROR      = '-';
+    const PREFIX_INTEGER    = ':';
+    const PREFIX_BULK       = '$';
+    const PREFIX_MULTI_BULK = '*';
+
+    const BUFFER_SIZE = 4096;
+
+    private $mbiterable;
+    private $serializer;
+
+    /**
+     *
+     */
+    public function __construct()
+    {
+        $this->mbiterable = false;
+        $this->serializer = new TextCommandSerializer();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function write(ComposableConnectionInterface $connection, CommandInterface $command)
+    {
+        $connection->writeBytes($this->serializer->serialize($command));
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function read(ComposableConnectionInterface $connection)
+    {
+        $chunk = $connection->readLine();
+        $prefix = $chunk[0];
+        $payload = substr($chunk, 1);
+
+        switch ($prefix) {
+            case '+':
+                switch ($payload) {
+                    case 'OK':
+                        return true;
+
+                    case 'QUEUED':
+                        return new ResponseQueued();
+
+                    default:
+                        return $payload;
+                }
+
+            case '$':
+                $size = (int) $payload;
+                if ($size === -1) {
+                    return null;
+                }
+
+                return substr($connection->readBytes($size + 2), 0, -2);
+
+            case '*':
+                $count = (int) $payload;
+
+                if ($count === -1) {
+                    return null;
+                }
+                if ($this->mbiterable) {
+                    return new MultiBulkResponseSimple($connection, $count);
+                }
+
+                $multibulk = array();
+
+                for ($i = 0; $i < $count; $i++) {
+                    $multibulk[$i] = $this->read($connection);
+                }
+
+                return $multibulk;
+
+            case ':':
+                return (int) $payload;
+
+            case '-':
+                return new ResponseError($payload);
+
+            default:
+                CommunicationException::handle(new ProtocolException(
+                    $connection, "Unknown prefix: '$prefix'"
+                ));
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function setOption($option, $value)
+    {
+        switch ($option) {
+            case 'iterable_multibulk':
+                $this->mbiterable = (bool) $value;
+                break;
+        }
+    }
+}