Form Processor

form tambah

<form action="" method="POST">
                        <div class="row">
                            <div class="col">
                                <div class="">
                                    <input type="hidden" id="id" name="id" class="form-control" placeholder="1">
                                </div>
                                <div class="mb-3">
                                    <label for="nama">Nama</label>
                                    <input type="text" id="nama" name="nama" class="form-control" placeholder="Intel Core i3 13100" required autocomplete="off">
                                </div>
                                <div class="mb-3">
                                    <label for="stok">Stok</label>
                                    <input type="number" id="stok" name="stok" class="form-control" placeholder="10" required autocomplete="off">
                                </div>
                            </div>
                            <div class="col">
                            </div>
                            <div class="mb-3">
                                <button class="btn ungu" name="submit">Simpan</button>
                                <a href="../processor/" class="btn btn-danger">Batal</a>
                            </div>
                        </div>
                    </form>

if (isset($_POST['submit'])) {
    $id = $_POST['id'];
    $nama = $_POST['nama'];
    $stok = $_POST['stok'];

    $query = "SELECT nama FROM processor WHERE nama = '$nama'";
    $result = mysqli_query($conn, $query);

    if (mysqli_num_rows($result) > 0) {
        $_SESSION['data'] = "sudah ada!";
    } else {
        $sql = "INSERT INTO processor (id, nama, stok) VALUES ('$id', '$nama', '$stok')";
        if (mysqli_query($conn, $sql)) {
            $_SESSION['data'] = "berhasil disimpan!";
            header("Location: ../processor");
            exit;
        } else {
            $_SESSION['data'] = "gagal disimpan!";
        }
    }
    mysqli_close($conn);
}