querying inside $form->input() array


             echo $form->input('field', array(
		    'type' => 'radio','legend'=>$r['Attribute']['label'],

		    'separator' => '--separator--',
		    'options' => array() 

How to query inside options to retrieve the options from the database for this corresponding Field..
like sending its attribute_id by $r['Attribute']['id']
and fetching the cooresponding choices for that attribute..
I have tried it with Ajax post

                             var ht = $.ajax({
                                              type: "GET",
                                              url: "http://localhost/FormBuilder/index.php/forms/viewChoices/"+attribute_id,
                                                                 async: false

               var myObject = eval('(' + ht + ')');

var data = myObject;var j=0;
 $.map(data.choices, function(i){ j++; alert(i.choice);

return i.choice;});

And it returns me the choices in the i.choice..
but i dont know how to place this inside the options array...
Please suggest me....