Post array is missing json from ajax request

Question

I'm trying to make a dynamic document previewer. The user can input certain document header options and based on their account information it will generate a document with a dynamic header. I eventually want to preview a full pdf but I am working on just the header right now.

What I am trying to do is make a page with a form that the user can fill out, then press a button to preview the header.

$.ajaxSetup({
type:       'POST',
timeout:    10000
});

$("#preview_header").click(function(){
    var full_url = //appropriate URL 

    var preview_data = {    
        "wsid":             "default",
        "page":             "default",
        "banner_area1":     "default",
        "banner_area2":     "default",
        "banner_area3":     "default",
        "uid":              "default",
        "fid":              "default",
        "cid":              "default",
        "assignment_type":  "default"
    };

    preview_data.wsid               = $("#worksheet_picker").val();
    preview_data.page               = $("#page_picker").val();
    preview_data.banner_area1       = $("#banner_area1").val();
    preview_data.banner_area2       = $("#banner_area2").val();
    preview_data.banner_area3       = $("#banner_area3").val();
    preview_data.uid                = $("#member_uid").val();
    preview_data.fid                = $("#family_id").val();
    preview_data.assignment_type    = 'family';
    preview_data.cid                = $("#class_id").val();

    var JSONText = JSON.stringify( preview_data );
    alert('Full JSON - ' + JSONText);

    $.ajax({
        async: true,
        url: full_url,
        data: { previewInfo : JSONText }, //Passes necessary form information
        dataType: 'json',
        success: function(output){
            var reply = output;
            if ( reply.status == "success" ){
                $("#preview").attr("src", reply.image );
            } else {
                alert('Failed to create image preview of the assignment.');
            } 
        } 
    });
});

As far as I can tell, the above method is working fine. It hits the right Codeigniter page and when the ajax method is set to return a hard coded image it works just fine. The AJAX seems to be well formatted but just in case here is what it outputs when I fill out forms with the corresponding values:

Full JSON - {"wsid":"4","page":"1","banner_area1":"link1",
"banner_area2":"link2","banner_area3":"link3",
"uid":"1","fid":"1","assignment_type":"family"}

So first off, let's start with what is working in the corresponding controller method for the ajax reply:

$data = array(
'status'    => 'success',
'image'     => //static image link
);

$this->output->set_content_type('text/javascript;charset=UTF-8');
echo json_encode($data);

But whenever I try to modify it like so:

$preview_data = json_decode($this->input->post('previewInfo'));

//Got this one
mail('me@gmail.com', 'Start Email', 'Some email' ); 
//Empty email
mail('me@gmail.com', 'Dump Post', var_dump($_POST)); 
//Empty email
mail('me@gmail.com', 'Post data', var_dump($preview_data) );
//returns an email with 1 for body
mail('me@gmail.com', 'Post data', print_r($this->input->post()) ); 
//returns an email with 1 for body
mail('me@gmail.com', 'Post data', 
     print_r($this->input->post('previewInfo')) ); 
//returns an email with 1 for body
mail('me@gmail.com', 'Post data', print_r($preview_data) );

$data = array(
'status'    => 'success',
'image'     => //static image link
);

$this->output->set_content_type('text/javascript;charset=UTF-8');
echo json_encode($data);

The modified one doesn't return the static data either. So it would seem that the post array is not being intialized properly. Anyone see the bug?

Answer 1

If you want to send your Ajax request with the post method, you need to set type to POST in your $.ajax options.

Also, async is true by default, so setting it is not necessary. Additionally, you should consider using .done and .fail as opposed to success and fail , as they are slated to be deprecated very soon.

Like so:

$.ajax({
    type: "POST",
    url: full_url,
    data: { previewInfo : JSONText }, //Passes necessary form information
    dataType: 'json'
}).done(function (output, textStatus, jqXHR) {
    var reply = output;
    if ( reply.status == "success" ){
        $("#preview").attr("src", reply.image );
    } else {
        alert('Failed to create image preview of the assignment.');
    } 
}).fail(function (jqXHR, textStatus, errorThrown) {
    // now you have the XHR, text status, and error to debug with
});

Answer 2

There was 2 problems that lead to the solution to this problem:

1)

As Austin and Gavin said: var_dump and print_r should not be outputting to the browser. The solution was to debug with firefox extensions / chrome.

2)

$preview_data = json_decode($this->input->post('previewInfo'));

was changed to

$preview_data = json_decode($this->input->post('previewInfo'), true);

The secondy optional parameter of json_decode is to tell the method whether you are expecting an associative object or a list of things. As it happens, I was reading in and wanted an associative array.