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/ServerInfo.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\Command;
+
+/**
+ * @link http://redis.io/commands/info
+ * @author Daniele Alessandri <suppakilla@gmail.com>
+ */
+class ServerInfo extends AbstractCommand
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function getId()
+    {
+        return 'INFO';
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function parseResponse($data)
+    {
+        $info      = array();
+        $infoLines = preg_split('/\r?\n/', $data);
+
+        foreach ($infoLines as $row) {
+            @list($k, $v) = explode(':', $row);
+
+            if ($row === '' || !isset($v)) {
+                continue;
+            }
+
+            if (!preg_match('/^db\d+$/', $k)) {
+                if ($k === 'allocation_stats') {
+                    $info[$k] = $this->parseAllocationStats($v);
+                    continue;
+                }
+
+                $info[$k] = $v;
+            } else {
+                $info[$k] = $this->parseDatabaseStats($v);
+            }
+        }
+
+        return $info;
+    }
+
+    /**
+     * Parses the reply buffer and extracts the statistics of each logical DB.
+     *
+     * @param  string $str Reply buffer.
+     * @return array
+     */
+    protected function parseDatabaseStats($str)
+    {
+        $db = array();
+
+        foreach (explode(',', $str) as $dbvar) {
+            list($dbvk, $dbvv) = explode('=', $dbvar);
+            $db[trim($dbvk)] = $dbvv;
+        }
+
+        return $db;
+    }
+
+    /**
+     * Parses the reply buffer and extracts the allocation statistics.
+     *
+     * @param  string $str Reply buffer.
+     * @return array
+     */
+    protected function parseAllocationStats($str)
+    {
+        $stats = array();
+
+        foreach (explode(',', $str) as $kv) {
+            @list($size, $objects, $extra) = explode('=', $kv);
+
+            // hack to prevent incorrect values when parsing the >=256 key
+            if (isset($extra)) {
+                $size = ">=$objects";
+                $objects = $extra;
+            }
+
+            $stats[$size] = $objects;
+        }
+
+        return $stats;
+    }
+}