How to pass student id from databtable button of ajax to open another page and get by post

Question

I'm a beginner at web developing I need help. I currently creating a evaluation system. I am doing the view feature which the admin can view the answers of those users who answer the evaluation.

<?php $userid=$_SESSION['id']; ?>

      <script>
        $(document).ready(function(){
            $('#empTable').DataTable({
                'processing': true,
                'serverSide': true,
                'serverMethod': 'post',
                'ajax': {
                    'url':'ajaxSearch.php'
                },
                'columns': [
                    { data: 'studentId' },
                    { data: 'fullname' },
                    { data: 'name' },
                    { data: 'eval' },
                    {"defaultContent": "<button>View</button>"},
                ]
            });
        $('#empTable tbody').on( 'click', 'button', function () {
            window.location.href = "viewEval.php"
        } );
        });
        </script>

I want to use the studentId to view the answers of every user who answer the evaluation. Thank you in advance