未在TCPDF中显示的标头

require_once('tcpdf/tcpdf.php');

class MYPDF extends TCPDF {
    // Page header
    public function Header() {
        // Set font
        $this->SetFont('helvetica', 'B', 20);
        // Title
        $this->Cell(0, 15, 'Document Title', 0, false, 'C', 0, '', 0, false, 'M', 'M');
    }
}

// Create new PDF document
$pdf = new MYPDF(PDF_PAGE_ORIENTATION, PDF_UNIT, PDF_PAGE_FORMAT, true, 'UTF-8', false);

// Set document information
$pdf->SetCreator(PDF_CREATOR);
$pdf->SetAuthor('Your Name');
$pdf->SetTitle('Document Title');
$pdf->SetSubject('Document Subject');
$pdf->SetKeywords('TCPDF, PDF, example, test, guide');

// Set default header data
$pdf->setHeaderData('', 0, 'Document Title', '');

// Set header and footer fonts
$pdf->setHeaderFont(Array(PDF_FONT_NAME_MAIN, '', PDF_FONT_SIZE_MAIN));
$pdf->setFooterFont(Array(PDF_FONT_NAME_DATA, '', PDF_FONT_SIZE_DATA));

// Set default monospaced font
$pdf->SetDefaultMonospacedFont(PDF_FONT_MONOSPACED);

// Set margins
$pdf->SetMargins(PDF_MARGIN_LEFT, PDF_MARGIN_TOP, PDF_MARGIN_RIGHT);
$pdf->SetHeaderMargin(PDF_MARGIN_HEADER);
$pdf->SetFooterMargin(PDF_MARGIN_FOOTER);

// Set auto page breaks
$pdf->SetAutoPageBreak(TRUE, PDF_MARGIN_BOTTOM);

// Set image scale factor
$pdf->setImageScale(PDF_IMAGE_SCALE_RATIO);

// Add a page
$pdf->AddPage();

// Set some content
$pdf->SetFont('helvetica', '', 12);
$pdf->Write(0, 'Hello World!');

// Output the HTML content
$pdf->Output('example.pdf', 'I');