Reload a php query that is included in html page when select option is pressed.

I have a index.php page that that uses this in the body.

<div id="live-area">
                            <?php include ('assets/php/multibox.php');?>
                                </div>

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In that multibox.php i have a div id container that loads my highcharts.
On that same multibox.php i have a query to load the table data.

I have a select option box that is filled by a mysql query on same page.

here is what the options look like

echo "<option value=index.php?id=$row[activity]/$row[app_name]>$row[app_name]</option>";

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So when they are clicked they reload the index.php (same page they are included on) and pass id.

I then have this on the multibox.php to check the id
if ($_GET['id'] == '')

So i can change the query based on that id so when the page loads it shows the chart with data for the selected.

SO... my question.

How can i just refresh that php with data for graph?

I did the following but it reloads the entire page into the live-area div.

echo "<select name=category value='' onchange=\"runthis(this)\"></option>";

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 <script type="text/javascript">

        function runthis(sel) {
            var page = sel.value;
        $.ajax({
            url: page,
            success: function (response) {
                $('#live-area').html(response);
            }
        });
        }
    </script>

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