Checkbox filetering not working - php

Question

I have a couple of checkboxes to filter the results from database but I have two problems, the first is that I am using $_POST variable and when I hit refresh I am getting a confirm form submission dialog, which I don't want as the user may hit refresh many times.
The 2nd part of it is that, if I replace $_POSTwith $_GET I don't see the the confirm message but the checkboxes don't work. Anyone has any idea?
<script type="text/javascript">
$(function(){
$('.checkbox').on('change',function(){
$('#form').submit();
});
});
</script>
<form id="id" method="post" action="">
<input type="checkbox" name="new" class="checkbox" <?php if(isset($_POST['new'])) echo "checked"; ?>/> New<br>
<input type="checkbox" name="used" class="checkbox" <?=(isset($_POST['used'])?' checked':'')?>/> Used<br>
<input type="checkbox" name="ref" class="checkbox" <?=(isset($_POST['ref'])?' checked':'')?>/> Refurbished<br>
</form>
if(isset($_GET['page']))
{
$page = $_GET['page'];
}
else
{
$page = 1;
}
$options = array(
'results_per_page' => 2,
'url' => 'products.php?search=' . urlencode($q) . '&page=*VAR*',
'db_handle' => $dbh
);
if (isset($_POST["ref"])) {
$arguments[] = " condition LIKE '%refur%' ";
}
if (isset($_POST["new"])) {
$arguments[] = " condition LIKE '%new%' ";
}
if (isset($_POST["used"])) {
$arguments[] = " condition LIKE '%use%' ";
}
if(!empty($arguments)) {
$str = implode(' or ',$arguments);
$qry = "SELECT * FROM products where " . $str . " ORDER BY id desc";
$paginate = new pagination($page, $qry, $options);
echo $qry;
}
else {
$paginate = new pagination($page, "SELECT * FROM products order by id desc", $options);
}

Answer 1

This is just an idea, using the classical/modern ajax approach for submitting. Assume that this page is called jqpost.php:
<script>
$(document).ready(function () {
$('.checkbox').on('change',function(){
//$('#form').submit();
var formdata = $("#form").serialize();
$.post("jqpost.php", formdata, function(data) {
$("#result").html("Post OK: " + formdata);
});
});
});
</script>
<form id="form" method="post" action="">
<input type="checkbox" name="new" class="checkbox" <?php if(isset($_POST['new'])) echo "checked"; ?>/> New<br>
<input type="checkbox" name="used" class="checkbox" <?=(isset($_POST['used'])?' checked':'')?>/> Used<br>
<input type="checkbox" name="ref" class="checkbox" <?=(isset($_POST['ref'])?' checked':'')?>/> Refurbished<br>
</form>
<div id="result"></div>
<?php
//...
?>
If a user clicks on a checkbox, jQuery will post data to jqpost.php script. In return, #result div will give a status text.
As a result, if the user presses the refresh button on browser, the form is not submitted again and again.