contoh session ajax

function session()
    {
        $this->session->set_flashdata('pembayaran', $_POST['pembayaran']);
    }

$("#npm").change(function(){

                            var value=$(this).val();
                            //if(value>0){
                            $.ajax({
                            data:{modul:'ikhwan',id:value},
                            success: function(respond){
                            //$("#jumlah_pembayaran").val(respond);
                            if(respond>0){
                                    $.post("<?php echo site_url();?>/select/session",{'pembayaran':respond});
                                    var output2= "Rp. " + parseInt(respond).toLocaleString();
                                    $("#jumlah_pembayaran").attr("placeholder", output2);
                                    $("#save").removeAttr("disabled");
                                }
                                else{
                                    var output1="NPM salah!";
                                    $("#jumlah_pembayaran").attr("placeholder", output1);
                                    $("#save").attr("disabled");
                                }

                            }
                            })
                            //}

                            });