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/MultiBulkResponse.php

@@ -0,0 +1,100 @@
+<?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\ResponseObjectInterface;
+
+/**
+ * Iterator that abstracts the access to multibulk replies and allows
+ * them to be consumed by user's code in a streaming fashion.
+ *
+ * @author Daniele Alessandri <suppakilla@gmail.com>
+ */
+abstract class MultiBulkResponse implements \Iterator, \Countable, ResponseObjectInterface
+{
+    protected $position;
+    protected $current;
+    protected $replySize;
+
+    /**
+     * {@inheritdoc}
+     */
+    public function rewind()
+    {
+        // NOOP
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function current()
+    {
+        return $this->current;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function key()
+    {
+        return $this->position;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function next()
+    {
+        if (++$this->position < $this->replySize) {
+            $this->current = $this->getValue();
+        }
+
+        return $this->position;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function valid()
+    {
+        return $this->position < $this->replySize;
+    }
+
+    /**
+     * Returns the number of items of the whole multibulk reply.
+     *
+     * This method should be used to get the size of the current multibulk
+     * reply without using iterator_count, which actually consumes the
+     * iterator to calculate the size (rewinding is not supported).
+     *
+     * @return int
+     */
+    public function count()
+    {
+        return $this->replySize;
+    }
+
+    /**
+     * Returns the current position of the iterator.
+     *
+     * @return int
+     */
+    public function getPosition()
+    {
+        return $this->position;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    abstract protected function getValue();
+}