form edit tugas php

<?php
    include('config.php');

    //ambil data dari url
    $id = $_GET['id'];

    $sql = 'SELECT * FROM calon_siswa WHERE id = '.$id;
    $query = mysqli_query($db_connection, $sql);
    $siswa = mysqli_fetch_assoc($query);

    if (mysqli_num_rows($query) < 1) {
        header('Location: list-siswa.php');
     }
?>

<!DOCTYPE html>
<html>
<head>
    <title>Formulir Edit</title>
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css">
</head>
<body>
    <header>
        <h3>Formulir Edit</h3>
    </header>

    <form method="post" action="proses-edit.php">
        <input type="hidden" name="id" value="<?php echo $siswa['id'] ?>">
        <p>
            <label class="form-label">Nama: </label>
            <input type="type" name="nama" placeholder="nama lengkap" class="form-control" value="<?php echo $siswa['nama'] ?>">
        </p>
        <p>
            <label class="form-label">Alamat: </label>
            <textarea name="alamat" class="form-control"><?php echo $siswa['alamat'] ?></textarea>
        </p>
        <p>
            <label>Jenis Kelamin: </label>
            <select name="jenis_kelamin">
                <option value="laki-laki" <?php echo ($siswa['jenis_kelamin'] == 'laki-laki') ? 'selected' : '' ?>>laki-laki</option>
                <option value="perempuan" <?php echo ($siswa['jenis_kelamin'] == 'perempuan') ? 'selected' : '' ?>>perempuan</option>
            </select>
        </p>
        <p>
            <label>Agama: </label>
            <select name="agama">
                <option <?php echo ($siswa['agama'] == 'islam') ? 'selected' : '' ?> value="islam">islam</option>
                <option <?php echo ($siswa['agama'] == 'kristen') ? 'selected' : '' ?> value="kristen">kristen</option>
                <option <?php echo ($siswa['agama'] == 'katolik') ? 'selected' : '' ?> value="katolik">katolik</option>
                <option <?php echo ($siswa['agama'] == 'hindu') ? 'selected' : '' ?> value="hindu">hindu</option>
                <option <?php echo ($siswa['agama'] == 'buddha') ? 'selected' : '' ?> value="buddha">buddha</option>
                <option <?php echo ($siswa['agama'] == 'konghucu') ? 'selected' : '' ?> value="konghucu">konghucu</option>
            </select>
        </p>
        <p>
            <label>Asal Sekolah: </label>
            <input type="type" name="sekolah_asal" placeholder="sekolah asal" class="form-control" value="<?php echo $siswa['sekolah_asal'] ?>">
        </p>
        <p>
            <button type="submit" class="btn btn-success">Perbarui</button>
        </p>
    </form>
</body>
</html>