使用数值jQuery PHP解析JSON

I am building a form that submits via Ajax. If our database updates successfully, the function in the controller returns numerical ids, and I would like to use these ids to change the view based on the result.

I am having difficulty parsing the ids that are returned from the controller. They are returned from the controller here:

foreach($update_pending as $product){
    $success_ids[] = $product['product_id'];
}

if(isset($success_ids)){
    echo json_encode($success_ids);
}else{
    echo json_encode(array('error'=>'Error!'));
}

The ids are returned like this: [129818,129819,129820]

Now I want to parse this so that I can change the view based on which ids were submitted. I referred to this question JQuery Parsing JSON array but I am still missing something.

When I submit the form I get error "Cannot read property 'length' of null "

Here is the jQuery function (EDIT: I added dataType: 'json', no change in result):

$(function () {
    $('form').on('submit', function (event) {
        var product = $(this).attr("data-id");

        event.preventDefault();

          $.ajax({
            type: 'POST',
            url: 'category_typeahead',
            data: $('form').serialize(),
                dataType: 'json',
            success: function (data) {
              if(data.error == undefined){
                alert(data);
                product_ids = $.parseJSON(data);

                for (var i=0, len=product_ids.length; i < len; i++) {
                    $(product_ids[i]).hide();
                }

              }else{
                if($('.error_true').length==0){
                    $('#error').append('<div class="alert alert-error error_true">Error text</div>');   
                }
                $('#error').show();
              } 
            }
          });

    });
  });

Try with this, ur var product_ids is not necessary

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js"></script>
<script type="text/javascript">
$(function () {
    $('form').on('submit', function (event) {
        var product = $(this).attr("data-id");

        event.preventDefault();// using this page stop being refreshing 

          $.ajax({
            type: 'POST',
            url: 'category_typeahead',
            data: $('form').serialize(),
                dataType: 'json',
            success: function (data) {
              if(data.error == undefined){
                data.forEach(function(entry){
                    $('#'+entry).hide();
                  });

              }else{
                if($('.error_true').length==0){
                    $('#error').append('<div class="alert alert-error error_true">Error text</div>');   
                }
                $('#error').show();
              } 
            }
          });

    });
  });
</script>