added a Doctrine DBAL extension

src/Silex/Extension/DoctrineExtension.php

+<?php
+
+/*
+ * This file is part of the Silex framework.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Silex\Extension;
+
+use Silex\Application;
+use Silex\ExtensionInterface;
+use Doctrine\DBAL\DriverManager;
+use Doctrine\DBAL\Configuration;
+use Doctrine\Common\EventManager;
+
+class DoctrineExtension implements ExtensionInterface
+{
+    public function register(Application $app)
+    {
+        $app['db.options'] = array_replace(array(
+            'driver'   => 'pdo_mysql',
+            'dbname'   => null,
+            'host'     => 'localhost',
+            'user'     => 'root',
+            'password' => null,
+        ), isset($app['db.options']) ? $app['db.options'] : array());
+
+        $app['db'] = $app->share(function() use($app) {
+            return DriverManager::getConnection($app['db.options'], $app['db.config'], $app['db.event_manager']);
+        });
+
+        $app['db.config'] = $app->share(function() {
+            return new Configuration();
+        });
+
+        $app['db.event_manager'] = $app->share(function() {
+            return new EventManager();
+        });
+
+        if (isset($app['db.dbal.class_path'])) {
+            $app['autoloader']->registerNamespace('Doctrine\\DBAL', $app['db.dbal.class_path']);
+        }
+
+        if (isset($app['db.common.class_path'])) {
+            $app['autoloader']->registerNamespace('Doctrine\\DBAL', $app['db.common.class_path']);
+        }
+    }
+}