Adding closures to compiled symfony 2 containers

generates.php

<?php

// Generated container classs
class DevProjectContainer extends Container
{
        /**
     * Gets the 'twig.loader' service.
     *
     * This service is shared.
     * This method always returns the same instance of the service.
     *
     * @return Twig_Loader_Filesystem A Twig_Loader_Filesystem instance.
     */
    protected function getTwig_LoaderService()
    {
        $this->services['twig.loader'] = $instance = new \Twig_Loader_Filesystem(array());

        $container = $this;
$closure = function(\Twig_Loader_Filesystem $loader) use ($container) {
                $loader->setPaths($container->getParameter('twig.template_dir'));
            };
$closure($instance);

        return $instance;
    }
}

SerializableCallable.php

<?php

/**
 * Serializable Closure
 *
 * Allows the serialization of a closure, specifically a Closure, for storage
 */
class SerializableCallable implements \Serializable
{
    /**
     * @var callable
     */
    protected $closure;

    /**
     * @param callable $closure Either a Closure object or a valid callable
     */
    public function __construct($closure)
    {
        if (is_array($closure) && is_object($closure[0])) {
            throw new \RuntimeException('Closures on object instances is not currently supported.');
        }
        else if (!is_callable($closure)) {
            throw new \RuntimeException('Closure is not callable.');
        }

        $this->closure = $closure;
    }

    /**
     * Invokes the stored closure
     */
    public function __invoke()
    {
        $args = func_get_args();
        return call_user_func_array($this->closure, $args);
    }

    /**
     * Gets $closure
     *
     * @return callable
     */
    public function getClosure()
    {
        return $this->closure;
    }
    
    public function __toString()
    {
        if (!($this->closure instanceof \Closure)) {
            // Is a normal closure, just serialize it
            return serialize(array('closure' => $this->closure));
        }

        $reflected = new \ReflectionFunction($this->closure);
        $code = $this->_getCode($reflected);
        $context = $reflected->getStaticVariables();
        
        $code = '$container = $this;' . "\n" . '$closure = ' . $code . ';' . "\n" . '$closure';
        
        return $code;
    }

    /**
     * @see Serializable::serialize()
     */
    public function serialize()
    {
        if (!($this->closure instanceof \Closure)) {
            // Is a normal closure, just serialize it
            return serialize(array('closure' => $this->closure));
        }

        $reflected = new \ReflectionFunction($this->closure);
        $code = $this->_getCode($reflected);
        $context = $reflected->getStaticVariables();

        return serialize(array('code' => $code, 'context' => $context));
    }

    /**
     * @see Serializable::unserialize()
     */
    public function unserialize($data)
    {
        $data = unserialize($data);
        if (!$data) {
            throw new \RuntimeException('Could not unserialize Closure. Unserialization failed.');
        }

        if (empty($data['closure'])) {
            $code = $data['code'];
            $context = $data['context'];

            extract($context);
            @eval("\$_closure = $code;");
            if (!isset($_closure) || !is_callable($_closure)) throw new \RuntimeException('Could not unserialize Closure. Invalid Closure specified.');
            $this->closure = $_closure;
        }
        else {
            $this->closure = $data['closure'];
        }
    }

    /**
     * Iterates on source files to return actual implementation of code
     *
     * @param \ReflectionFunction $reflected
     */
    protected function _getCode(\ReflectionFunction $reflected)
    {
        $file = new \SplFileObject($reflected->getFileName());
        $file->seek($reflected->getStartLine() - 1);
        $code = '';
        while ($file->key() < $reflected->getEndLine()) {
            $code .= $file->current();
            $file->next();
        }
        $begin = strpos($code, 'function');
        $end = strrpos($code, '}');
        $code = substr($code, $begin, $end - $begin + 1);

        return $code;
    }
}

setup.php

<?php

// Inside AppKernel.php somewhere

$getTemplateDir = new SerializableCallable(function(\Twig_Loader_Filesystem $loader) use ($container) {
    $loader->setPaths($container->getParameter('twig.template_dir'));
});

$container->setParameter('twig.template_dir', $this->getRootDir() . '/views');
$container->register('twig.loader', 'Twig_Loader_Filesystem')
    ->addArgument(array())
    ->setConfigurator($getTemplateDir);
    
$container->compile();
$this->dumpContainer($cache, $container, $class, 'Container');