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/Transaction/AbortedMultiExecException.php

@@ -0,0 +1,45 @@
+<?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\Transaction;
+
+use Predis\PredisException;
+
+/**
+ * Exception class that identifies MULTI / EXEC transactions aborted by Redis.
+ *
+ * @author Daniele Alessandri <suppakilla@gmail.com>
+ */
+class AbortedMultiExecException extends PredisException
+{
+    private $transaction;
+
+    /**
+     * @param MultiExecContext $transaction Transaction that generated the exception.
+     * @param string           $message     Error message.
+     * @param int              $code        Error code.
+     */
+    public function __construct(MultiExecContext $transaction, $message, $code = null)
+    {
+        parent::__construct($message, $code);
+        $this->transaction = $transaction;
+    }
+
+    /**
+     * Returns the transaction that generated the exception.
+     *
+     * @return MultiExecContext
+     */
+    public function getTransaction()
+    {
+        return $this->transaction;
+    }
+}