Symfony 1.4和ajax参数“null”

i'm trying to use ajax,but i cant reach my variables in my php.

On my symfony page i have :

$.ajax({
   type: "POST",
   url: "agenda/data",
   data: { title : title}
});

and in action.class.php => executeData function i try to get the parameter like that : $title = $request->getParameter('title'); but it always return null . why?

how can i get my javascript variables into my action.class.php (i just want to insert them in db, and i don't want to get null parameter lol)?