Laravel display "FPDF error: No page has been added yet" - laravel

Question

I am using the fpdf library for my laravel project. I create a class for the header and footer function. Then call thess functions on my pdf controller. I encounter this error "FPDF error: No page has been added yet" and I have no idea where this error came from. Can you teach me on how to fix this bug/error. Thanks in advance.
Codes from my controller
namespace App\Http\Controllers;
use Illuminate\Http\Request;
use Codedge\Fpdf\Fpdf\Fpdf;
use App\Personnel;
use App\Classes\PDFClass;
class PFTReportController extends Controller
{
public function postPFTReport(Request $request)
{
$pdf = new FPDF();
$pdf->AddPage('P', 'A4');
$pdf->Ln(4);
$pdf->SetFont('Arial', '', 12);
// Call the header for this report
$pdfClass = new PDFClass();
$header = $pdfClass->Header();
$pdf->Cell(0, 4, 'Sample Report', 0, 1, 'C');
$pdf->Ln(2);
$pdf->Output();
exit;
}
}
Code of the class
namespace App\Classes;
use Codedge\Fpdf\Fpdf\Fpdf;
class PDFClass extends Fpdf
{
protected $B = 0;
protected $I = 0;
protected $U = 0;
protected $HREF = '';
// Page header
function Header()
{
$this->SetFont('Arial', '', 11);
$this->Cell(0, 2, 'Line 1', 0, 1, 'C');
$this->Cell(0, 8, 'Line 2', 0, 1, 'C');
$this->SetFont('Arial', 'B', 12);
$this->Cell(0, 1, 'Line 3', 0, 1, 'C');
$this->Cell(0, 8, 'Line 4', 0, 1, 'C');
$this->SetFont('Arial', '', 12);
$this->Cell(0, 1, 'Line 5', 0, 1, 'C');
$this->Ln(8);
}
}

Answer 1

You create 2 class instances. The first is FPDF where you add a page:
$pdf = new FPDF();
$pdf->AddPage('P', 'A4');
$pdf->Ln(4);
$pdf->SetFont('Arial', '', 12);
...then you create a new one and simply call your Header() method manually:
$pdfClass = new PDFClass();
$header = $pdfClass->Header();
This doesn't make sense and at this point the error is thrown, because you call several methods in Header() which should output content to a page but you didn't added one before.
You should only use PDFClass and you also should not call the Header() method manually because it is called internally automatically.
public function postPFTReport(Request $request)
{
$pdf = new PDFClass();
$pdf->AddPage('P', 'A4'); // NOW THE HEADER() METHOD IS INVOKED AUTOMATICALLY IN THIS CALL
$pdf->Ln(4);
$pdf->SetFont('Arial', '', 12);
$pdf->Cell(0, 4, 'Sample Report', 0, 1, 'C');
$pdf->Ln(2);
$pdf->Output();
exit;
}