Symfonys 2 app_dev.php给出一个空白页面，而app.php完美运行

I'm trying to start a new project with Symfony2. I started with a simple Hello world. Controller:

class DefaultController extends Controller
{
public function indexAction()
{
    $name = 'world';
    return $this->render('MyowntestBundle:Default:index.html.twig', array('name' => $name));
}
}

View:

{% extends "::base.html.twig" %}

{% block body %}

Hello {{ name }}!

{% endblock %}

When i open site through app.php everything is ok, but opening app_dev.php results in a blank, white page. Nothing in apache main error log, nothing in vhost error log and app/logs/dev.log is empty too.

Whats wrong?

app_dev only works when testing on the same server. meaning you're on your WAMP/XAMP etc..

To enable using app_dev.php, open it and comment out the following:

       if (isset($_SERVER['HTTP_CLIENT_IP'])
   || isset($_SERVER['HTTP_X_FORWARDED_FOR'])
   || !in_array(@$_SERVER['REMOTE_ADDR'], array('127.0.0.1', 'fe80::1', '::1'))

) { header('HTTP/1.0 403 Forbidden'); exit('You are not allowed to access this file. Check '.basename(FILE).' for more information.'); }

you can find app_dev.php in the web/app_dev.php directory.

Good luck !

Problems gone after updating PHP to 5.4. Dont know what was exactly wrong.