[HELP] Input field tapi apabila filed kosong, tidak bisa tersimpan

<?php include 'header.php'; ?>



<h3><span class="glyphicon glyphicon-briefcase"></span>  Data Kupon Blonjo Bejo</h3>

<button style="margin-bottom:20px" data-toggle="modal" data-target="#myModal" class="btn btn-info col-md-2"><span class="glyphicon glyphicon-plus"></span>Tambah Data Kupon</button>

<br/>

<br/>





<?php 

$per_hal=10;

$jumlah_record=mysql_query("SELECT COUNT(*) from kupon");

$jum=mysql_result($jumlah_record, 0);

$halaman=ceil($jum / $per_hal);

$page = (isset($_GET['page'])) ? (int)$_GET['page'] : 1;

$start = ($page - 1) * $per_hal;

?>

<div class="col-md-12">

 <table class="col-md-2">

  <tr>

   <td>Jumlah Record</td>  

   <td><?php echo $jum; ?></td>

  </tr>

  <tr>

   <td>Jumlah Halaman</td> 

   <td><?php echo $halaman; ?></td>

  </tr>

 </table>

 <a style="margin-bottom:10px" href="lap_kupon.php" target="_blank" class="btn btn-default pull-right"><span class='glyphicon glyphicon-print'></span>  Cetak</a>

</div>

<form action="cari_act.php" method="get">

 

  <div class="input-group col-md-5 col-md-offset-7"> <span class="input-group-addon" id="basic-addon1"><span class="glyphicon glyphicon-search"></span></span> 

    <input type="text" class="form-control" placeholder="Cari Dengan No Kupon .." aria-describedby="basic-addon1" name="cari">

  </div>

</form>

<br/>

<table class="table table-hover">

 <tr>

  <th width="20" class="col-md-1">No</th>

  <th width="72" class="col-md-4">No Kupon</th>

  <th width="105" class="col-md-3">Nama Customer</th>

  <th width="30" class="col-md-1">NIK KTP/SIM</th>

  <th width="48" class="col-md-1">Alamat</th>

  <!-- <th class="col-md-1">Sisa</th>  -->

  <th width="110" class="col-md-3">Opsi</th>

 </tr>

 <?php 

 if(isset($_GET['cari'])){

  $cari=mysql_real_escape_string($_GET['cari']);

  $barang=mysql_query("select * from kupon where nokupon like '$cari' or namacustomer like '$cari'");

 }else{

  $barang=mysql_query("select * from kupon limit $start, $per_hal");

 }

 $no=1;

 while($b=mysql_fetch_array($barang)){



  ?>

  <tr>

   <td><?php echo $no++ ?></td>

   <td><?php echo $b['nokupon'] ?></td>

   <td><?php echo $b['namacustomer'] ?></td>

   <td><?php echo $b['nik'] ?></td>

   <td><?php echo $b['alamat'] ?></td>

   <td>

    <a href="det_kupon.php?id=<?php echo $b['id']; ?>" class="btn btn-info">Detail</a>

    <a href="edit_kupon.php?id=<?php echo $b['id']; ?>" class="btn btn-warning">Edit</a>

    <a>Hapus</a>

   </td>

  </tr>  

  <?php 

 }

 ?>

 <tr>

  

    <td colspan="4"> </td>

 <td>  </td>

    <td>  </td>

 </tr>

</table>

<ul class="pagination">   

   <?php 

   for($x=1;$x<=$halaman;$x++){

    ?>

    <li><a href=""><?php echo $x ?></a></li>

    <?php

   }

   ?>      

  </ul>

<!-- modal input -->

<div id="myModal" class="modal fade">

 <div class="modal-dialog">

  <div class="modal-content">

   <div class="modal-header">

    <button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button>

    <h4 class="modal-title">Tambah Data Kupon</h4>

   </div>

   <div class="modal-body">

    <form method="post" action="tmb_kupon_act.php" >

     

     <div class="form-group form-group-lg has-feedback">

      <label>Nama Customer</label>

      <input name="namacustomer" type="text" class="form-control textbox" placeholder="Nama Customer ..">

      <i class="form-control-feedback"></i>

       <span class="text-warning" ></span>

     </div>

     <div class="form-group">

      <label>NIK KTP/SIM</label>

      <input name="nik" type="text" class="form-control" placeholder="NIK KTP/SIM ..">

     </div>

     <div class="form-group">

      <label>Alamat</label>

      <input name="alamat" type="text" class="form-control" placeholder="Alamat Cust ..">

     </div>

     <div class="form-group">

      <label>Nomor Telpon</label>

      <input name="notelp" type="text" class="form-control" placeholder="Nomor Telepon ..">

     </div>

     

      <div class="form-group">

       <label>Tanggal Pembelian </label>

       <input name="tgl_pembelian" type="text" class="form-control" id="tgl" autocomplete="off">

      </div>

      

      <div class="form-group">

         <label>Cara Pembayaran </label> 

                <select name="cara_pembayaran">

                            <option value="Tunai">Tunai</option>

                            <option value="EDC Mandiri">EDC Mandiri</option>

                            <option value="EDC Bank Lain">EDC Bank Lain</option>

                        </select>

</select>

          

    

     <p> </p>

     

        </div>

      

     <div 

      class="form-group">

      <label>Nama Toko</label>

      <input name="namatoko" type="text" class="form-control" placeholder="Nama Toko ..">

     </div>

     

     <div class="form-group">

      <label>No Kupon</label>

      <input name="nokupon" type="text" class="form-control" placeholder="No Kupon ..">

     </div>

     

     <div

     class="form-group">

     <strong>Nominal Belanja</strong> 

          <input name="nominalbelanja" type="int" class="form-control" id="txt1" >

          <strong>Jumlah 

          Kupon </strong> 

          <input  name="jumlahkupon" type="int" id="nominalbelanja" >

          <strong>Kupon</strong> 

            [removed]

     function sum() {

           var txtFirstNumberValue = document.getElementById('txt1').value;



           var result = parseInt(txtFirstNumberValue) / parseInt('50000');

           if (!isNaN(result)) {

            document.getElementById('nominalbelanja').value = result;

            }

      }

    [removed]

     </div>



     

     



     <div class="form-group">

      

          <label></label>

        </div>

     

         



    <div class="modal-footer">

     <button type="button" class="btn btn-default" data-dismiss="modal">Batal</button>

     <input type="submit" class="btn btn-primary" value="Simpan">

    </div>

   </form>

  </div>

 </div>

</div>



[removed]

  $(document).ready(function(){

   $("#tgl").datepicker({dateFormat : 'yy/mm/dd'});       

  });

 [removed]



<?php include 'footer.php';  ?>

<?php 

include 'config.php';



// menyimpan data kedalam variabel



$nokupon=$_POST['nokupon'];

$namacustomer=$_POST['namacustomer'];

$nik=$_POST['nik'];

$alamat=$_POST['alamat'];

$notelp=$_POST['notelp'];

$tgl_pembelian=$_POST['tgl_pembelian'];

$cara_pembayaran=$_POST['cara_pembayaran'];

$namatoko=$_POST['namatoko'];

$nominalbelanja=$_POST['nominalbelanja'];



// query SQL untuk insert data



mysql_query("insert into kupon values('','$nokupon','$namacustomer','$nik','$alamat','$notelp','$tgl_pembelian','$cara_pembayaran','$namatoko','$nominalbelanja')");

header("location:kupon.php");



 ?>