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/KeySort.php

@@ -0,0 +1,117 @@
+<?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/sort
+ * @author Daniele Alessandri <suppakilla@gmail.com>
+ */
+class KeySort extends AbstractCommand implements PrefixableCommandInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function getId()
+    {
+        return 'SORT';
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function filterArguments(Array $arguments)
+    {
+        if (count($arguments) === 1) {
+            return $arguments;
+        }
+
+        $query = array($arguments[0]);
+        $sortParams = array_change_key_case($arguments[1], CASE_UPPER);
+
+        if (isset($sortParams['BY'])) {
+            $query[] = 'BY';
+            $query[] = $sortParams['BY'];
+        }
+
+        if (isset($sortParams['GET'])) {
+            $getargs = $sortParams['GET'];
+
+            if (is_array($getargs)) {
+                foreach ($getargs as $getarg) {
+                    $query[] = 'GET';
+                    $query[] = $getarg;
+                }
+            } else {
+                $query[] = 'GET';
+                $query[] = $getargs;
+            }
+        }
+
+        if (isset($sortParams['LIMIT']) &&
+            is_array($sortParams['LIMIT']) &&
+            count($sortParams['LIMIT']) == 2) {
+
+            $query[] = 'LIMIT';
+            $query[] = $sortParams['LIMIT'][0];
+            $query[] = $sortParams['LIMIT'][1];
+        }
+
+        if (isset($sortParams['SORT'])) {
+            $query[] = strtoupper($sortParams['SORT']);
+        }
+
+        if (isset($sortParams['ALPHA']) && $sortParams['ALPHA'] == true) {
+            $query[] = 'ALPHA';
+        }
+
+        if (isset($sortParams['STORE'])) {
+            $query[] = 'STORE';
+            $query[] = $sortParams['STORE'];
+        }
+
+        return $query;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function prefixKeys($prefix)
+    {
+        if ($arguments = $this->getArguments()) {
+            $arguments[0] = "$prefix{$arguments[0]}";
+
+            if (($count = count($arguments)) > 1) {
+                for ($i = 1; $i < $count; $i++) {
+                    switch ($arguments[$i]) {
+                        case 'BY':
+                        case 'STORE':
+                            $arguments[$i] = "$prefix{$arguments[++$i]}";
+                            break;
+
+                        case 'GET':
+                            $value = $arguments[++$i];
+                            if ($value !== '#') {
+                                $arguments[$i] = "$prefix$value";
+                            }
+                            break;
+
+                        case 'LIMIT';
+                            $i += 2;
+                            break;
+                    }
+                }
+            }
+
+            $this->setRawArguments($arguments);
+        }
+    }
+}