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/ServerSlowlog.php

@@ -0,0 +1,50 @@
+<?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/slowlog
+ * @author Daniele Alessandri <suppakilla@gmail.com>
+ */
+class ServerSlowlog extends AbstractCommand
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function getId()
+    {
+        return 'SLOWLOG';
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function parseResponse($data)
+    {
+        if (is_array($data)) {
+            $log = array();
+
+            foreach ($data as $index => $entry) {
+                $log[$index] = array(
+                    'id' => $entry[0],
+                    'timestamp' => $entry[1],
+                    'duration' => $entry[2],
+                    'command' => $entry[3],
+                );
+            }
+
+            return $log;
+        }
+
+        return $data;
+    }
+}