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/Command/HashScan.php

@@ -0,0 +1,84 @@
+<?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\Command;
+
+/**
+ * @link http://redis.io/commands/hscan
+ * @author Daniele Alessandri <suppakilla@gmail.com>
+ */
+class HashScan extends PrefixableCommand
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function getId()
+    {
+        return 'HSCAN';
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function filterArguments(Array $arguments)
+    {
+        if (count($arguments) === 3 && is_array($arguments[2])) {
+            $options = $this->prepareOptions(array_pop($arguments));
+            $arguments = array_merge($arguments, $options);
+        }
+
+        return $arguments;
+    }
+
+    /**
+     * Returns a list of options and modifiers compatible with Redis.
+     *
+     * @param  array $options List of options.
+     * @return array
+     */
+    protected function prepareOptions($options)
+    {
+        $options = array_change_key_case($options, CASE_UPPER);
+        $normalized = array();
+
+        if (!empty($options['MATCH'])) {
+            $normalized[] = 'MATCH';
+            $normalized[] = $options['MATCH'];
+        }
+
+        if (!empty($options['COUNT'])) {
+            $normalized[] = 'COUNT';
+            $normalized[] = $options['COUNT'];
+        }
+
+        return $normalized;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function parseResponse($data)
+    {
+        if (is_array($data)) {
+            $data[0] = (int) $data[0];
+            $fields = $data[1];
+            $result = array();
+
+            for ($i = 0; $i < count($fields); $i++) {
+                $result[$fields[$i]] = $fields[++$i];
+            }
+
+            $data[1] = $result;
+        }
+
+        return $data;
+    }
+}