使用jQuery，AJAX和PHP单击复选框时更新MySQL字段

I need a checkbox to update a MySQL field from a 1 to 0 and vice versa when clicked. I want to use jQuery/AJAX and PHP to do this so I do not have to have the page re-loaded. I placed the code below but I cannot get it to work. I feel that I am very close.

Note: I know mysql_query is deprecated. This is an older project and I will be converting it soon but need this to work for now.

The form:

if($list_row['online'] == 0) {
    echo '<input type="checkbox" name="online" id="' . $list_row['id'] . '" data-toggle="toggle" checked>&nbsp;';
} else {
    echo '<input type="checkbox" name="online" id="' . $list_row['id'] . '" data-toggle="toggle">&nbsp;';

                        }

The jQuery:

 <script>
$('.online').mousedown(function() {

    var id    = $(this).attr('id');

    if($(this).attr('checked')) {
        var online = 1;
    } else {
        var online = 0;
    }

    $.ajax({
        type:'GET',
        url:'processes/process_item_online.php?',
        data:'id= ' + id + '&online='+online
    });

 });
 </script>

The PHP:

include '../connect.php';

// START IF LOGGED IN
  session_start();

if (!isset($_SESSION['is_logged_in'])) {

    header("location: login.php");

} else {

    $login = true;

}


 $id = $_GET['id'];
 $online = $_GET['online'];

 mysql_query("UPDATE `store_items` SET online=$online WHERE id='$id'");

Problem solved by using the $(document).ready(function() { code before the jquery.