Chris C is correct, but not at that point:
if(isset($_POST['submit'])){ <-- this open brace is not being closed
$nama=$_POST['nama'];
$jawatan=$_POST['jawatan'];
$telefon=$_POST['telefon'];
$sem=$_POST['sem'];
$cgpa=$_POST['cgpa'];
$matrik=$_POST['matrik'];
$penasihat=$_POST['penasihat'];
$email=$_POST['email'];
$telefonpenasihat=$_POST['telefonpenasihat'];
$pengiring1=$_POST['pengiring1'];
$telefonpengiring1=$_POST['telefonpengiring1'];
$pengiring2=$_POST['pengiring2'];
$telefonpengiring2=$_POST['telefonpengiring2'];
$sql="update `butir` set nama='$nama', jawatan='$jawatan', telefon='$telefon', sem=$sem, cgpa=$cgpa, matrik=$matrik, penasihat='$penasihat', email='$email', telefonpenasihat='$telefonpenasihat', pengiring1='$pengiring1', telefonpengiring1='$telefonpengiring1', pengiring2='$pengiring2', telefonpengiring2='$telefonpengiring2'";
$result=mysqli_query($con,$sql);
if($result){ <-----------------------------these two
echo "Updated successfully"; } <-------match
else{ <------------------------and these two
die(mysqli_error($con));
} <----------------------------also match