my echo "<tr> </tr"; error when i use bootsrap :     echo "<tr class ='a'>
    <td>".$data->id."</td>
	<td>".$data->nis."</td>
	<td>".$data->nama."</td>
	<td>".$data->jenis_kelamin."</td>
	<td>".$data->telp."</td>
	<td>".$data->alamat."</td>
	<td><a class="btn btn-warning" href="'.base_url("siswa/ubah/".$data->id).'">Ubah</a></td>
	<td><a class="btn btn-danger" href="'.base_url("siswa/hapus/".$data->id).'">Hapus</a></td>
    </tr>";

its error when i use bootstrap in my coding, how to keep this from error?

					