<?php
                    session_start();
                    include_once("connection.php");
                    if(isset($_POST['login'])){
                        $stud_no = $_POST["stud_no"];
                      $password = $_POST["pword"];
                        $name = mysqli_real_escape_string($con, $stud_no);
                        $password = mysqli_real_escape_string($con, $password);
                        $select_user="SELECT * FROM student_accounts WHERE stud_no ='$stud_no' AND password ='$password'";
                        $run_user = mysqli_query($con, $select_user);
                        $check_user = mysqli_num_rows($run_user);
                        if($check_user > 0){
                        $_SESSION['stud_no'] = $stud_no;
                            header('location: home.php');
                        }

                        else{
                             echo '<script>$("#myModal").modal()</script>';

                        }
                    }

                    ?>

<div id="myModal" class="modal fade" role="dialog">
  <div class="modal-dialog">

    <!-- Modal content-->
    <div class="modal-content">
      <div class="modal-header">
        <button type="button" class="close" data-dismiss="modal">&times;</button>
        <h4 class="modal-title">Modal Header</h4>
      </div>
      <div class="modal-body">
        <p>Some text in the modal.</p>
      </div>
      <div class="modal-footer">
        <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
      </div>
    </div>

  </div>
</div>