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/Iterator/MultiBulkResponseSimple.php

@@ -0,0 +1,89 @@
+<?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\Iterator;
+
+use Predis\Connection\SingleConnectionInterface;
+
+/**
+ * Streams a multibulk reply.
+ *
+ * @author Daniele Alessandri <suppakilla@gmail.com>
+ */
+class MultiBulkResponseSimple extends MultiBulkResponse
+{
+    private $connection;
+
+    /**
+     * @param SingleConnectionInterface $connection Connection to Redis.
+     * @param int                       $size       Number of elements of the multibulk reply.
+     */
+    public function __construct(SingleConnectionInterface $connection, $size)
+    {
+        $this->connection = $connection;
+        $this->position = 0;
+        $this->current = $size > 0 ? $this->getValue() : null;
+        $this->replySize = $size;
+    }
+
+    /**
+     * Handles the synchronization of the client with the Redis protocol
+     * then PHP's garbage collector kicks in (e.g. then the iterator goes
+     * out of the scope of a foreach).
+     */
+    public function __destruct()
+    {
+        $this->sync(true);
+    }
+
+    /**
+     * Synchronizes the client with the queued elements that have not been
+     * read from the connection by consuming the rest of the multibulk reply,
+     * or simply by dropping the connection.
+     *
+     * @param bool $drop True to synchronize the client by dropping the connection.
+     *                   False to synchronize the client by consuming the multibulk reply.
+     */
+    public function sync($drop = false)
+    {
+        if ($drop == true) {
+            if ($this->valid()) {
+                $this->position = $this->replySize;
+                $this->connection->disconnect();
+            }
+        } else {
+            while ($this->valid()) {
+                $this->next();
+            }
+        }
+    }
+
+    /**
+     * Reads the next item of the multibulk reply from the server.
+     *
+     * @return mixed
+     */
+    protected function getValue()
+    {
+        return $this->connection->read();
+    }
+
+    /**
+     * Returns an iterator that reads the multi-bulk response as
+     * list of tuples.
+     *
+     * @return MultiBulkResponseTuple
+     */
+    public function asTuple()
+    {
+        return new MultiBulkResponseTuple($this);
+    }
+}