Jquery JSON Ajax Callback Not Working - Cakephp

Question

I'm trying to write a simple JSON post and the callback alert does not show up no matter what I do. I used firebugs to see if the post was getting any response and "SHOE" returns. So why is the alert not working in the callback?

view code:

$('#GaragePartAddfrompartlistForm').click(function() { 
      var item = "CHEESE"; 
  $.post("garage_parts/getlastid", { 'item' : item }, 
   function(data){ 
     alert(data.result); 
   }, "json"); 
    });

controller code:

function getlastid() { 
    $newid = "SHOE"; 
        $array = array('result' => $newid); 
        echo json_encode($array); 
    }

Answer 1

You should try setting the HTTP header in the response with:

header("Content-type: application/json")

or

header("Content-type: text/plain")

jQuery might not be handling your response because it is not getting the expected type back.

Your response code would then be:

function getlastid() { 
    header("Content-type: text/plain");
    $newid = "SHOE"; 
    $array = array('result' => $newid); 
    echo json_encode($array); 
}

Hope this helps!

Answer 2

Don't forget to set empty layout for Ajax responses:

function getlastid() { 
    $this->layout = 'ajax';
    ...

Answer 3

I'm not too familiar with cake, but I use codeigniter (which is similar)...

One thing I have noticed with framework like these, is that when you send out a json response using echo json_encode($array) you have to enter exit(); immediately on the next line. Other wise, the framework sends out headers indicating a html mime-type.

May be that is the case with cake too, in any case it's worth a try...

Answer 4

Make sure you're setting debug to 0 in beforeFilter, use RequestHandler component to check if it is an ajax request.

Use RequestHandler

var $components = array(..., 'RequestHandler', ...);

set debug to 0 if it's an ajax request

function beforeFilter()
{
    if ($this->RequestHandler->isAjax()) {
        Configure::write('debug', 0);
    }
}

and in your function

function getlastid() 
{
    $this->autoRender = false;
    $this->autoLayout = false;

    $newid = "SHOE";
    $response = array('result' => $newid); 

    $this->header('Content-Type: application/json');
    echo json_encode($response);
    return;
}

If you echo json and don't set debug to 0, cake will add the execution time at the end and it will not be a valid json response, preventing jQuery to properly read it.

As an extra, usually i set some more stuff in the $response, so i can better handle it.

function getLastId()
{
    ...
    $response = array('success' => false);

    ... code ...
    if ($my_code_is_good) {
        $response['success'] = true;
        $response['data'] = $my_code_result;
    }

    ...
}

Hope this helps

Answer 5

I found that with my symfony/PHP application, ordinary text responses with no HTML characters (either using a null or a 'json' dataType) would trigger the success callback. However if the server does not output anything except headers, the success callback is not called (which I would consider a bug).

Furthermore, if the server response contained HTML characters (<> etc), again the callback would not be called unless the context type is explicitly set to text/html. This also removed annoying < pre> tags added incorrectly by jQuery as well as preventing jQuery from converting the response to HTML entities (& lt;& gt; etc).