form sederhana

<?php session_start();?>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Contoh</title>
</head>
<body>
<form  method="post" action="beli.php" >
<table width="400" bgcolor="#00FF55"  cellpadding="4">
<tr><td> beli</td><td align="right"><input type="text" name="beli" /></td></tr>
<tr><td>banyak pasangan</td><td align="right"><input type="text" name="bpasangan" /></td></tr>
<tr><td>
  <input type="submit" name="laju" value="HITUNG"/>
  </td></tr>
</table>
</form>
<?php
if(isset($_POST['laju']) && $_POST['laju']=="HITUNG"){
  $harga_satuan=7000;
  $total_beli=$total_jumlah=0;
  echo "<table border=\"1\">\n"
      ."<tr><th>No</th><th>Beli</th><th>Jumlah</th></tr>\n";
  $_SESSION['beli'][]=isset($_POST['beli'])?$_POST['beli']:0;
  $_SESSION['bpasangan'][]=isset($_POST['bpasangan'])?$_POST['bpasangan']:0;
  if(isset($_SESSION['beli']) && !empty($_SESSION['beli'])){
    for($i=0;$i<count($_SESSION['beli']);$i++){
      $total_beli+=$_SESSION['beli'][$i];
      $total_jumlah+=$_SESSION['bpasangan'][$i];
      echo "<tr><th>".($i+1)."</th><th>".$_SESSION['beli'][$i]."</th><th>".$_SESSION['bpasangan'][$i]."</th></tr>\n";
    }
  }
  echo "<tr><th>Total</th><th>".$total_beli."</th><th>".$total_jumlah."</th></tr>\n"
      ."</table>\n";
}
if(isset($_POST['hapus']) && $_POST['hapus']=="hapus"){
  unset($_SESSION['beli']);
  unset($_SESSION['bpasangan']);
}
?>
<form  method="post" action="beli.php" >
  <input type="submit" name="hapus" value="hapus"/>
</form>
</body>
</html>