I had this code:

require_once __DIR__ . '/vendor/autoload.php';
use DompdfDompdf;

add_shortcode('gerar-pdf', 'pdf');
function pdf() {
    ob_start();
    include( get_stylesheet_directory() . '/includes/certificado.php' );
    $html = ob_get_clean();

    $dompdf = new Dompdf();
    $dompdf->loadHtml($html);
    $dompdf->render();
    $dompdf->stream("certificado.pdf");
}

to transform my html + css code into a PDF, but the file that be generated every goes corrupted, i alread try to remove the include and put a html directly like <p> Hello </p>, but it’s also return corrupted. How can i solve this?

I’ve tried to clear buffer and use html directly