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/Pipeline/StandardExecutor.php

@@ -0,0 +1,123 @@
+<?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\Pipeline;
+
+use Iterator;
+use SplQueue;
+use Predis\ResponseErrorInterface;
+use Predis\ResponseObjectInterface;
+use Predis\ServerException;
+use Predis\Command\CommandInterface;
+use Predis\Connection\ConnectionInterface;
+use Predis\Connection\ReplicationConnectionInterface;
+
+/**
+ * Implements the standard pipeline executor strategy used
+ * to write a list of commands and read their replies over
+ * a connection to Redis.
+ *
+ * @author Daniele Alessandri <suppakilla@gmail.com>
+ */
+class StandardExecutor implements PipelineExecutorInterface
+{
+    protected $exceptions;
+
+    /**
+     * @param bool $exceptions Specifies if the executor should throw exceptions on server errors.
+     */
+    public function __construct($exceptions = true)
+    {
+        $this->exceptions = (bool) $exceptions;
+    }
+
+    /**
+     * Allows the pipeline executor to perform operations on the
+     * connection before starting to execute the commands stored
+     * in the pipeline.
+     *
+     * @param ConnectionInterface $connection Connection instance.
+     */
+    protected function checkConnection(ConnectionInterface $connection)
+    {
+        if ($connection instanceof ReplicationConnectionInterface) {
+            $connection->switchTo('master');
+        }
+    }
+
+    /**
+     * Handles a response object.
+     *
+     * @param  ConnectionInterface     $connection
+     * @param  CommandInterface        $command
+     * @param  ResponseObjectInterface $response
+     * @return mixed
+     */
+    protected function onResponseObject(ConnectionInterface $connection, CommandInterface $command, ResponseObjectInterface $response)
+    {
+        if ($response instanceof ResponseErrorInterface) {
+            return $this->onResponseError($connection, $response);
+        }
+
+        if ($response instanceof Iterator) {
+            return $command->parseResponse(iterator_to_array($response));
+        }
+
+        return $response;
+    }
+
+    /**
+     * Handles -ERR responses returned by Redis.
+     *
+     * @param  ConnectionInterface    $connection The connection that returned the error.
+     * @param  ResponseErrorInterface $response   The error response instance.
+     * @return ResponseErrorInterface
+     */
+    protected function onResponseError(ConnectionInterface $connection, ResponseErrorInterface $response)
+    {
+        if (!$this->exceptions) {
+            return $response;
+        }
+
+        // Force disconnection to prevent protocol desynchronization.
+        $connection->disconnect();
+        $message = $response->getMessage();
+
+        throw new ServerException($message);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function execute(ConnectionInterface $connection, SplQueue $commands)
+    {
+        $this->checkConnection($connection);
+
+        foreach ($commands as $command) {
+            $connection->writeCommand($command);
+        }
+
+        $values = array();
+
+        while (!$commands->isEmpty()) {
+            $command = $commands->dequeue();
+            $response = $connection->readResponse($command);
+
+            if ($response instanceof ResponseObjectInterface) {
+                $values[] = $this->onResponseObject($connection, $command, $response);
+            } else {
+                $values[] = $command->parseResponse($response);
+            }
+        }
+
+        return $values;
+    }
+}