Silex logout URL

app.php

$app['security.firewalls'] = array(
	'login' => array(
        'pattern' => '^/login$',
		'anonymous' => true,
    ),
    'admin' => array(
        'pattern' => '^/admin',
    	'form' => array(
    			'login_path' => '/login', 
    			'check_path' => '/admin/login_check'),
    	'logout' => array('logout_path' => '/admin_logout', 'target_url' => '/admin'),
    	'users' => $app->share(function () use ($app) {
    		return new UserProvider($app);
		}),
    ),	
);

I have been trying to figure out how to do this for a while. Thank you!