CodeIgniter 3: Export Excel Dari HTML

composer require phpoffice/phpspreadsheet

$config['composer_autoload'] = 'vendor/autoload.php';

<h3>LAPORAN DATA REGISTRASI</h3>

<table>
    <thead>
        <tr>
            <th>No</th>
            <th>Tanggal</th>
            <th>Nama Siswa</th>
            <th>Nomor WA</th>
        </tr>
    </thead>
    <tbody>
        <?php $no = 1 ?>
        <?php foreach ($registrasi as $row) : ?>
            <tr>
                <td><?= $no++ ?></td>
                <td><?= $row['tanggal'] ?></td>
                <td><?= $row['nama_siswa'] ?></td>
                <td><?= $row['nomor_wa'] ?></td>
            </tr>
        <?php endforeach; ?>
    </tbody>
</table>

use PhpOffice\PhpSpreadsheet\Reader\Html;
use PhpOffice\PhpSpreadsheet\Style\Alignment;
use PhpOffice\PhpSpreadsheet\Style\Border;
use PhpOffice\PhpSpreadsheet\Writer\Xlsx;

class Laporan extends CI_Controller
{
    // ...

    public function excel()
    {
        // load data dari model
        $data['registrasi'] = $this->registrasi_model->findAll();

        // view template
        $html = $this->load->view('excel', $data, TRUE);

        $reader = new Html();
        $spreadsheet = $reader->loadFromString($html);

        $worksheet = $spreadsheet->getActiveSheet();

        // merge cell A1 sampai D1
        // karena tabel yang digunakan 4 kolom
        // maka header nya di merge 4 cell
        $worksheet->mergeCells('A1:D1');

        // setelah di merge lalu di center horizontal
        $worksheet->getStyle('A1:D1')->getAlignment()->setHorizontal(Alignment::HORIZONTAL_CENTER);

        // tambahkan baris kosong di row ke-2
        // supaya setelah header gak langsung ke tabel
        $worksheet->insertNewRowBefore(2, 1);

        // set style untuk semua cell
        $style = [
            'font' => ['size' => 12],
            'alignment' => ['vertical' => Alignment::VERTICAL_TOP],
        ];
        $worksheet->getStyle($worksheet->calculateWorksheetDimension())->applyFromArray($style);

        // set lebar kolom auto size, jadi lebih rapi
        foreach ($worksheet->getColumnIterator() as $column) {
            $worksheet->getColumnDimension($column->getColumnIndex())->setAutoSize(true);
        }

        // tambahkan border tapi hanya untuk tabel/datanya
        // A3 berarti baris ketiga, karena yang pertama header, kedua baris kosong
        // range sampai cell D karena empat kolom datanya
        $worksheet->getStyle('A3:D' . $worksheet->getHighestRow())->applyFromArray([
            'borders' => [
                'allBorders' => [
                    'borderStyle' => Border::BORDER_THIN
                ]
            ]
        ]);

        // header untuk auto download, filename bisa diganti untuk nama file hasil export
        header("Content-Type: application/vnd.ms-excel");
        header("Content-Disposition: attachment; filename=laporan-registrasi.xlsx");
        header("Cache-Control: max-age=0");

        $writer = new Xlsx($spreadsheet);
        $writer->save("php://output");

        exit();
    }
}