Debugging jQuery ajax 500 Internal server error

Question

My working CodeIgniter site is giving a 500 Internal Server Error while hosting it on MediaTemple. It is happening during a jQuery Ajax call.

I have no idea what could have gone wrong. Is the error from the controller or the model? My Ajax call:

$.ajax({
    url: "<?php echo site_url('invites/save_email') ?>",
    type: 'POST',
    data: form_data,
    success: function(msg) {
    window.location.href = "<?php echo site_url('invites/moreinvites')?>"
        return true;
    },
    error: function (xhr, ajaxOptions, thrownError) {
        alert(xhr.status);
        alert(thrownError);
        alert(xhr.responseText);
    }
});

xhr.responseText has returned me <p>The action you have requested is not allowed.</p>. But what does that mean?

Answer 1

You can try using alert(xhr.responseText); or console.log(xhr.responseText); (the later will show up in your browser console e.g. firebug) in your error callback, doing so you can get the message associated with the exception (if any).

error: function (xhr, ajaxOptions, thrownError) {
           alert(xhr.status);
           alert(xhr.responseText);
           alert(thrownError);
       }

or

error: function (xhr, ajaxOptions, thrownError) {
           console.log(xhr.status);
           console.log(xhr.responseText);
           console.log(thrownError);
       }