我一直得到Undefined索引：kamar_id和Undefined index：kota_id所以我有点想知道我的脚本是否正确？ [重复]

<?php

    include '../koneksi.php';

    if(isset($_POST['submit_add'])){
        $nama = $_POST['nama'];
        $alamat = $_POST['alamat'];
        $kamar_id = $_POST['kamar_id'];
        $kota_id = $_POST['kota_id'];
        $sql = "INSERT INTO penghuni (nama,alamat,kamar_id,kota_id) VALUES ('$nama','$alamat','$kamar_id','$kota_id')";
        if(!$conn->query($sql))
            die('Tambah Penghuni Gagal'.$sql);
        else
            header("Location: penghuni.php");
    }

    if(isset($_POST['submit_edit'])){
        $id_old = $_POST['id_old'];
        $kamar_id = $_POST['kamar_id'];
        $kota_id = $_POST['kota_id'];
        $nama = $_POST['nama'];
        $alamat = $_POST['alamat'];
        $sql = "UPDATE penghuni SET nama='$nama', alamat='$alamat', kamar_id='$kamar_id', kota_id='$kota_id' WHERE id='$id_old'";
        if(!$conn->query($sql))
            die('Update Penghuni Gagal'.$sql);
        else
            header("Location: penghuni.php");
    }

    // $id = $_GET['id'];
    if(isset($_POST['submit_delete'])){
        $id_old = $_POST['id_old'];
        $sql = "DELETE FROM penghuni
                WHERE id='$id_old';";
        if (!$conn->query($sql))
            die('Hapus Penghuni Gagal'.$sql);
        else{
            header("Location: penghuni.php");
            exit();
        }
    }
?>

</div>