Bolt\Provider\TwigServiceProvider::register PHP Method

    public function register(Application $app)
    {
        if (!isset($app['twig'])) {
            $app->register(new \Silex\Provider\TwigServiceProvider());
        }
        $app['twig.loader.bolt_filesystem'] = $app->share(function ($app) {
            $loader = new FilesystemLoader($app['filesystem']);
            $themePath = 'theme://' . $app['config']->get('theme/template_directory');
            $loader->addPath($themePath, 'theme');
            $loader->addPath('bolt://app/theme_defaults', 'theme');
            $loader->addPath('bolt://app/view/twig', 'bolt');
            /** @deprecated Deprecated since 3.0, to be removed in 4.0. */
            $loader->addPath($themePath);
            $loader->addPath('bolt://app/theme_defaults');
            $loader->addPath('bolt://app/view/twig');
            return $loader;
        });
        // Insert our filesystem loader before native one
        $app['twig.loader'] = $app->share(function ($app) {
            return new \Twig_Loader_Chain([$app['twig.loader.array'], $app['twig.loader.bolt_filesystem'], $app['twig.loader.filesystem']]);
        });
        // Handlers
        $app['twig.handlers'] = $app->share(function (Application $app) {
            return new \Pimple(['admin' => $app->share(function () use($app) {
                return new Handler\AdminHandler($app);
            }), 'array' => $app->share(function () use($app) {
                return new Handler\ArrayHandler($app);
            }), 'html' => $app->share(function () use($app) {
                return new Handler\HtmlHandler($app);
            }), 'image' => $app->share(function () use($app) {
                return new Handler\ImageHandler($app);
            }), 'record' => $app->share(function () use($app) {
                return new Handler\RecordHandler($app);
            }), 'routing' => $app->share(function () use($app) {
                return new Handler\RoutingHandler($app);
            }), 'text' => $app->share(function () use($app) {
                return new Handler\TextHandler($app);
            }), 'user' => $app->share(function () use($app) {
                return new Handler\UserHandler($app);
            }), 'utils' => $app->share(function () use($app) {
                return new Handler\UtilsHandler($app);
            }), 'widget' => $app->share(function () use($app) {
                return new Handler\WidgetHandler($app);
            })]);
        });
        // Add the Bolt Twig Extension.
        $app['twig'] = $app->share($app->extend('twig', function (\Twig_Environment $twig, $app) {
            $twig->addExtension(new TwigExtension($app, $app['twig.handlers'], false));
            $twig->addExtension($app['twig.extension.asset']);
            $twig->addExtension($app['twig.extension.http_foundation']);
            if (isset($app['dump'])) {
                $twig->addExtension(new DumpExtension($app['dumper.cloner'], $app['dumper.html'], $app['users'], $app['config']->get('general/debug_show_loggedoff', false)));
            }
            return $twig;
        }));
        $app['twig.extension.asset'] = $app->share(function ($app) {
            return new AssetExtension($app['asset.packages'], $app['twig.extension.http_foundation']);
        });
        $app['twig.extension.http_foundation'] = $app->share(function ($app) {
            return new HttpFoundationExtension($app['request_stack'], $app['request_context']);
        });
        // Twig options
        $app['twig.options'] = function () use($app) {
            $options = [];
            // Should we cache or not?
            if ($app['config']->get('general/caching/templates')) {
                $key = hash('md5', $app['config']->get('general/theme'));
                $options['cache'] = $app['resources']->getPath('cache/' . $app['environment'] . '/twig/' . $key);
            }
            if (($strict = $app['config']->get('general/strict_variables')) !== null) {
                $options['strict_variables'] = $strict;
            }
            return $options;
        };
        $app['safe_twig.bolt_extension'] = function () use($app) {
            return new TwigExtension($app, $app['twig.handlers'], true);
        };
        $app['safe_twig'] = $app->share(function ($app) {
            $loader = new \Twig_Loader_String();
            $twig = new \Twig_Environment($loader);
            $twig->addExtension($app['safe_twig.bolt_extension']);
            return $twig;
        });
    }