gistfile1.php

<?
class HasAccessScreen extends Screen
{
	public function before($controller,$metadata,&$data)
	{
		// make sure we have a valid user id from current session
		if (!$uid=$controller->session->id)
			throw new InvalidParametersException();
		
		// fetch the forum ID
		if (!$id=$controller->request->input->get_num($metadata->key))
			throw new NotFoundException();
			
		// find the forum model in the database
		$forum=filter($metadata->to)->
			->id->equals($id)
			->owner_id->equals($uid)
			->first();
		
		// no forum, no love!
		if (!$forum)
			throw new NotFoundException();
			
		// ...
	}
}