if checkbox is checked php

If checkbox is checked I want to store a value in php variable and for unchecked store another value

        <script>
        $('input[type="checkbox"][name="change"]').change(function() {
                if(this.checked) {
                    <?php $sql="SELECT * FROM `order` ORDER BY sl_no ASC"?>
                } else {
                    <?php $sql="SELECT * FROM `order` ORDER BY sl_no DESC"?>
                }
            });
        </script>

        <input type="checkbox" name="change">