Undefined index in php when updating form action [duplicate]

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• PHP: “Notice: Undefined variable” and “Notice: Undefined index” 13 answers

I got the message "undefined index Nama and NIM" when I try to update my form. here is the code

<?php
include "koneksi.php";
$Nama = $_POST["Nama"];
$NIM = $_GET["NIM"];
$Tanggal = $_POST['thn']."-".$_POST['bln']."-".$_POST['tgl'];
$ProgramStudi = $_POST["ProgramStudi"];
$Strata = $_POST["Strata"];
$Sponsor = $_POST["Sponsor"];
$TanggalUjian = $_POST["TanggalUjian"];
$TanggalLulus= $_POST["TanggalLulus"];
$AlamatRumah = $_POST["AlamatRumah"];
$Telp = $_POST["Telp"];
$Judul = $_POST["Judul"];

if (empty($Nama))
{   
    die("Isikan Nama!");
} 
elseif(empty($NIM))
{
    die("Isikan NIM!");
}
else //bisa tambahkan pengecekan yang lain jika perlu
{
    //proses upload photo jika ada
    if (!empty($_FILES["photo"]["tmp_name"]))
    {
        $namafolder="photo/"; //tempat menyimpan file
        $jenis_gambar=$_FILES['photo']['type'];
        if($jenis_gambar=="image/jpeg" || $jenis_gambar=="image/jpg" || $jenis_gambar=="image/gif" || $jenis_gambar=="image/png")
        {           
            $photo = $namafolder . basename($_FILES['photo']['name']);       
            if (!move_uploaded_file($_FILES['photo']['tmp_name'], $photo)) 
            {
               die("Gambar gagal dikirim");
            }
            //Hapus photo yang lama jika ada
            $res = mysql_query("select photo from skl_ where NIM='$NIM' LIMIT 1");
            $d=mysql_fetch_object($res);
            if (strlen($d->photo)>3)
            {
                if (file_exists($d->photo)) unlink($d->photo);
            }                   
            //update photo dengan yang baru
            mysql_query("UPDATE skl_ SET photo='$photo' WHERE NIM='$NIM' LIMIT 1");
        } 
        else { die("Jenis gambar yang anda kirim salah. Harus .jpg .gif .png"); }
    } //end if cek file upload
    $myqry="UPDATE skl_ SET Nama='$Nama',Tanggal='$Tanggal',".
            "ProgramStudi='$ProgramStudi',Strata='$Strata',Sponsor='$Sponsor',TanggalUjian='$TanggalUjian',TanggalLulus='$TanggalLulus',AlamatRumah='$AlamatRumah',Telp='Telp',Judul='Judul' WHERE NIM='$NIM' LIMIT 1";
    mysql_query($myqry) or die(mysql_error());
    header("location:laporan-data-mahasiswa2a.php");
    exit;
}       
?>

what's wrong with that codes? how can I fix them? I've spent much hours to solve that problem but I cant. help me to solve these codes please. thankyou