autocomplete problem

autocomplete problem

Hi everybody! I'm trying to use autocomplete via php&mysql with multiple input. I used multiple:true parameter but nothing has happened... Can you tell me what to do? Here's an example of my code:

var feature = $('#new_feature').clone(true);
$('#new_feature').remove().removeAttr('id');
$('#add_new_feature').click(function() {
$(feature).clone(true).appendTo('ul.new_features').fadeIn('slow').find("input[name*=new_feature_name]").focus();
return false;
});

$('input[name*="options"]').each(function(index) {
f_id = $(this).closest('li').attr('feature_id');
ac = $(this).autocomplete({
serviceUrl:'ajax/options_autocomplete.php',
  params: {feature_id:f_id},
noCache: false
});
});