How can I pass an extra variable with this JSON and jQuery code?

Question

I am trying to set up an AJAX file upload script with jQuery and JSON.

I have some experience with AJAX and jQuery, but have never used JSON in my life.

While going through this tutorial, I found that their method of retrieving uploaded files was to get all the files from the database.

This does not suit my current needs. This will be part of a form for writing articles to the database, so the script needs to work only with attachments associated with the article being created.

I basically had to create a DB table for attachment sessions which I use to determine the attachments that are currently being worked with.

This is fine, however, I now need a way to pass an extra variable for the session id to the jQuery script.

I have encoded the JSON data in my PHP script, but now how do I access the certain variable in the jQuery script? In the code below, I will indicate where I encoded the JSON data, and also where I would like to add that data in the jQuery script.

PS: This is in CodeIgniter.

This is the PHP script

function upload_file()
{         
    $status = '';
    $msg = '';

    $config = array(
        'upload_path' => FCPATH.'attachments',
        'allowed_types' => 'jpg|gif|png',
        'min_height' => ($this->session->flashdata('img_min_height')) ? $this->session->flashdata('img_min_height') : 0,
        'min_width' => ($this->session->flashdata('img_min_width')) ? $this->session->flashdata('img_min_width') : 0,
        'max_height' => ($this->session->flashdata('img_max_height')) ? $this->session->flashdata('img_max_height') : 0,
        'max_width' => ($this->session->flashdata('img_max_width')) ? $this->session->flashdata('img_max_width') : 0,
        'max_size' => 300,
        'encrypt_name' => TRUE
    );

    $this->load->library('upload', $config);

    if(!$this->upload->do_upload('user_files')){

        $status = 'error';
        $msg = $this->upload->display_errors('', '');

    } else {

        $data = $this->upload->data();
        $this->attachment->create($data);

        if($this->attachment->error == NULL){

            $status = "success";
            $msg = "File uploaded.";
            $session_id = $this->attachment->_session_id;

        } else {

            unlink($data['full_path']);
            $status = "error";
            $msg = $this->attachment->error;
            $session_id = '';

        }

    }

    @unlink($_FILES['user_files']);     

    echo json_encode(array('status' => $status, 'msg' => $msg, 'session_id' => $session_id )); **//I added the session id variable here.**

}

This is the jQuery script that gets the uploaded files:

function refresh_files()
{
    $.get('./upload/files/') //The session ID should go at the end of this URL...
    .success(function (data){
        $('#files').html(data);
    });
}

Answer 1

You simply add an extra parameter next to the url.

Reference: http://api.jquery.com/jquery.get/

   $.get('./upload/files/', required_data_here)
    .success(function (data){
        $('#files').html(data);
   });

Then in your server-side script:

<?php
  var sess_id = $_GET['your_variable_here'];
?>

Here's an example from the reference:

$.get( "test.php", { name: "John", time: "2pm" } );