OOP

#edit_action.php
<?php
    require 'library.php';
    if (isset($_POST['submit'])) {

        $id = $_GET['kode'];
        $buku = $_POST['buku'];
        $penerbit = $_POST['penerbit'];

        $up = $buku->updateBuku($id, $judul, $penerbit);
        if ($up == 'Seccess') {
            header('Location:index.php');
        }else{
            echo "failed!";
        }
    }
?>

#library.php
<?php

    /**
     * library.php
     * connection, show, add, edit, delete!
     */

    class library{

        public function __construct()
        {
            $this->db = new PDO('mysql:host=localhost;dbname=crudbuku', 'root', '');
        }

        public function addBuku($judul, $penerbit)
        {
            $sql = "INSERT INTO buku(buku, penerbit) VALUES('$judul', '$penerbit')";
            $query = $this->db->query($sql);

            if (!$query) {
                return "failed!";
            }else{
                return "success!";
            }
        }

        public function showBuku()
        {
            $sql = "SELECT * FROM buku";
            $query = $this->db->query($sql);
            return $query;
        }

        public function editBuku($id)
        {
            $sql = "SELECT * FROM buku WHERE id = '$id'";
            $query = $this->db->query($sql);
            return $query;
        }

        public function updateBuku($id, $judul, $penerbit)
        {
            $sql = "UPDATE buku SET buku = '$judul', penerbit = '$penerbit' WHERE id = '$id'";
            $query = $this->db->query($sql);
            if (!$query) {
                return "failed!";
            }else{
                return "success!";
            }
        }

    }

#edit.php

<?php include_once('includes/header.php'); ?>
<div class="row">
    <div class="grid">
        <div class="col-12">
            <div class="col">
                <?php
                    require 'library.php';
                    if (isset($_GET['kode'])) {

                        $buku = new Library();
                        $book = $buku->editBuku($_GET['kode']);
                        $row = $book->fetch(PDO::FETCH_OBJ);
                    }
                ?>
                <form action="edit_action.php" method="POST">
                    <label for="fname">Judul Buku</label>
                    <input type="text" id="fname" name="judul" value="<?php echo $row->buku; ?>">
                    <label for="lname">Penerbit</label>
                    <input type="text" id="lname" name="penerbit" value="<?php echo $row->penerbit; ?>">
                    <input type="submit" value="Submit" name="submit">
                    <?php echo $row->id; ?>
                </form>
            </div>
        </div>
    </div>
</div>
<?php include_once('includes/footer.php'); ?>