Kok gak muncul

//ini file koneksi.php
<?php
$host="localhost";
$username="root";
$password="";
$db_name="oop";

mysql_connect($host,$username,$password,$db_name) or DIE("Koneksi ke DB gagal!");
mysql_select_db($db_name)or DIE ("Nama DB tidak ada");
?>


//ini file class.php
<?php
require 'koneksi.php';
//Class Database
class operasi{

		function lihatdata(){
		$tampil=mysql_query("SELECT nim,thang,nama,alamat From mahasiswa;");
		while($row=mysql_fetch_array($tampil))
			$data[]=$row;
		return $data;
	}

}

?>



//ini file yang manggil show.php
<?php
require_once 'classoperasi.php';
$hasil=new operasi();
$hasil->lihatdata();
?>
 <table width="500" border="1" >

         <tr >
<th><center><b>No</b></center></th>
<th><center><b>Nim</b></center></th>
<th><center><b>Tahun</b></center></th>
<th><center><b>Nama</b></center></th>
<th><center><b>Alamat</b></center></th>
         </tr>

<?php
$no=1;
foreach ($hasil as $data) {
    ?>
    <tr>
        <td><center><?php echo $no; ?></center></td>
        <td><center><?php echo $data['nim']; ?></center></td>
        <td><center><?php echo $data['thang']; ?></center></td>
        <td><center><?php echo $data['nama']; ?></center></td>
        <td><center><?php echo $data['alamat']; ?></center></td>
    </tr>
    <?php
    $no++;}
    ?>