PHP website: How to restrict uploaded files to only the requesting student in an online school document processing system?

good day. I am a total noob but I would like to ask for you help by asking this question. We are currently building a php website from scratch which is an Online School Documents Processing system where the students can request for their files online and the admin will approve the request by uploading the file and the student can see and download the file. My problem is when the admin uploads the requested file, all students who have signed up can see the file. I want it to be exclusive to the student who requested the file. How should I do that? THank you so much.

THis is the code for the uploading of the document in the admin:

   <?php include('main_header/header.php');?>
     <?php include('left_sidebar/sidebar.php');?>
    <div class="dashboard-wrapper">
        <div class="container-fluid  dashboard-content">
            <div class="row">
                <div class="col-xl-12 col-lg-12 col-md-12 col-sm-12 col-12">
                    <div class="page-header">
                         <h2 class="pageheader-title"><i class="fa fa-fw fa-file-word"></i> Add Document </h2>
                        <div class="page-breadcrumb">
                            <nav aria-label="breadcrumb">
                                <ol class="breadcrumb">
                                    <li class="breadcrumb-item"><a href="#" class="breadcrumb-link">Dashboard</a></li>
                                    <li class="breadcrumb-item active" aria-current="page">Document</li>
                                </ol>
                            </nav>
                        </div>
                    </div>
                </div>
            </div>                
                <div class="row">
                    <div class="col-xl-12 col-lg-12 col-md-12 col-sm-12 col-12">
                                <div class="card influencer-profile-data">
                                    <div class="card-body">
                                         <div class="" id="message"></div>
                                        <form id="validationform" name="docu_form" data-parsley-validate="" novalidate="" enctype="multipart/form-data" >
                                            <div class="form-group row">
                                                <label class="col-12 col-sm-3 col-form-label text-sm-right"><i class="fa fa-file-word"></i> Document Info</label>
                                            </div>
                                            <div class="form-group row">
                                                <label class="col-12 col-sm-3 col-form-label text-sm-right">Upload Document</label>
                                                <div class="col-12 col-sm-8 col-lg-6">
                                                    <input data-parsley-type="alphanum" type="file" alt="document_name" id="document_name" accept=".docx, .doc, .pptx, .ppt, .xlsx, .xls, .pdf, .odt" required="" placeholder="" class="form-control">
                                                    <footer style="font-size: 11px"><b>File Type:</b><font color="red"><i>.docx .doc .pptx .ppt .xlsx .xls .pdf .odt</i></font></footer>
                                                </div>
                                            </div>
                                            <div class="form-group row">
                                                <label class="col-12 col-sm-3 col-form-label text-sm-right">Description</label>
                                                <div class="col-12 col-sm-8 col-lg-6">
                                                    <input data-parsley-type="alphanum" alt="document_decription" type="text" required="" placeholder="" class="form-control">
                                                </div>
                                            </div>

                                            </div>
                                            <div class="form-group row text-right">
                                                <div class="col col-sm-10 col-lg-9 offset-sm-1 offset-lg-0">
                                                    <input type="text" alt="student_id" value="<?= $_SESSION['student_id'];?>" class="form-control" hidden>
                                                    <button type="button" class="btn btn-space btn-primary" id="btn-docu">Submit</button>
                                                </div>
                                            </div>
                                        </form>
                                    </div>
                                </div>
                        </div>
                    </div>
                </div>
       
        </div>
    </div>
</div>

<script src="../assets/vendor/jquery/jquery-3.3.1.min.js"></script>
<script src="../assets/vendor/bootstrap/js/bootstrap.bundle.js"></script>
<script src="../assets/vendor/parsley/parsley.js"></script>
<script src="../assets/libs/js/main-js.js"></script>
<script>
$('#form').parsley();
</script>
 <script type="text/javascript">
    $(document).ready(function(){
      var firstName = $('#firstName').text();
      var lastName = $('#lastName').text();
      var intials = $('#firstName').text().charAt(0) + $('#lastName').text().charAt(0);
      var profileImage = $('#profileImage').text(intials);
    });
</script>
<script>
(function() {
    'use strict';
    window.addEventListener('load', function() {
        // Fetch all the forms we want to apply custom Bootstrap validation styles to
        var forms = document.getElementsByClassName('needs-validation');
        // Loop over them and prevent submission
        var validation = Array.prototype.filter.call(forms, function(form) {
            form.addEventListener('submit', function(event) {
                if (form.checkValidity() === false) {
                    event.preventDefault();
                    event.stopPropagation();
                }
                form.classList.add('was-validated');
            }, false);
        });
    }, false);
})();
</script>

                    <script>
       document.addEventListener('DOMContentLoaded', () => {
          let btn = document.querySelector('#btn-docu');
          btn.addEventListener('click', () => {

          const document_name = document.querySelector('input[id=document_name]').value; 
          const document_decription = document.querySelector('input[alt=document_decription]').value;
          const student_id = document.querySelector('input[alt=student_id]').value;

         var data = new FormData(this.form);

            data.append('document_name', $('#document_name')[0].files[0]);
            data.append('document_decription', document_decription);
            data.append('student_id', student_id);


            if (document_name === '' || document_decription === '') {//continue niyo nalang ito
              $('#message').html('<div class="alert alert-danger"> Required All Fields!</div>');
              } else {
                  $.ajax({
                      url: '../init/controllers/add_document.php',
                      type: "POST",
                      data: data,
                      processData: false,
                      contentType: false,

                      async: false,
                      cache: false,

                      success: function(data) {
                          $('#message').html(data);

                      },
                      error: function(data) {
                          console.log("Failed");
                      }
                  });
              }     

          });
      });
  </script>