Why can't this script retrieve the data to another php file

Question

I made my table autoload using ajax once a user enters data in the to_date date box but it seems like I can't retrieve the data to another PHP file using this script. I'm still a beginner in coding so please be easy on me. Please help. Thanks!

<script type="text/javascript">
    $(document).ready(function(){
        // load_data(); 

        function load_data(fromdate, todate)
        {
            $.ajax({
                url:"vehicle_table.php",
                method:"POST",
                data:{fromdate:fromdate, todate:todate},
                success:function(data) {
                    $('.activity').html(data);
                }
            });
        }
  
        let to_date = document.querySelector("#to_date");
        let from_date = document.querySelector("#from_date");
        to_date.addEventListener("change", stateHandle);
        from_date.addEventListener("change", stateHandle);
        to_date.disabled = true;
        var fromdate = $('#from_date').datepicker({  format: 'yyyy-mm-dd'});
        var todate = $('#to_date').datepicker({  format: 'yyyy-mm-dd'});

        function stateHandle() {
            if(document.querySelector("#from_date").value === "") {
                to_date.disabled = true;
                $('.activity').html('');          
            } else {     
                if(document.querySelector("#to_date").value === ""){
                    to_date.disabled = false;
                    $('.activity').html('');
                } else {          
                    to_date.disabled = false;
                    $.ajax({
                        url:"vehicle_table.php",
                        method:"POST",
                        data:{fromdate:fromdate, todate:todate},
                        success:function(data) {
                            $('.activity').html(data);
                        }
                    });

            }     
            to_date.disabled = false;
            $('.activity').html('');
        } 
    } 
    $(document).ready(function(){  
        $.datepicker.setDefaults({  
            dateFormat: 'yy-mm-dd'   
        });  
    });
});
</script>

These are my from_date and to_date.

<form action="vehicle_table.php" method="post">
    <div class="col-md-4">
      <label for="from_date"></label>
      <input type="date" name="from_date" id="from_date" class="form-control datepicker input" placeholder="From Date" />
    </div>
    <div class="col-md-4">
      <label for="to_date"></label>
      <input type="date" name="to_date" id="to_date" class="form-control datepicker input2" placeholder="To Date" />
    </div>                                         
    </div>
  </form>

I didn't see any error but it didn't get pass through the

if(isset($_POST['fromdate'],$_POST['todate']))