FPDF error: Some data has already been output, can't send PDF

Question

I am using the fpdf library for my project, and I'm using this to extend one of the drupal module. These lines

$pdf = new FPDF(); $pdf->AddPage(); $pdf->SetFont('Arial','B',16); $pdf->Cell(40,10,'Hello World!'); $pdf->Output(); 

give me an error: FPDF error: Some data has already been output, can't send PDF

I tried creating this in a separate file outside the drupal area name test.php and when viewed it worked. Anyone here know why this don't work? Or anyone here can point me a right pdf library which I can use in drupal to view HTML to PDF format.

Answer 1

For fpdf to work properly, there cannot be any output at all beside what fpdf generates. For example, this will work:

<?php $pdf = new FPDF(); $pdf->AddPage(); $pdf->SetFont('Arial','B',16); $pdf->Cell(40,10,'Hello World!'); $pdf->Output(); ?> 

While this will not (note the leading space before the opening <? tag)

 <?php $pdf = new FPDF(); $pdf->AddPage(); $pdf->SetFont('Arial','B',16); $pdf->Cell(40,10,'Hello World!'); $pdf->Output(); ?> 

Also, this will not work either (the echo will break it):

<?php echo "About to create pdf"; $pdf = new FPDF(); $pdf->AddPage(); $pdf->SetFont('Arial','B',16); $pdf->Cell(40,10,'Hello World!'); $pdf->Output(); ?> 

I'm not sure about the drupal side of things, but I know that absolutely zero non-fpdf output is a requirement for fpdf to work.

Answer 2

add ob_start (); at the top and at the end add ob_end_flush();

<?php     ob_start();     require('fpdf.php');     $pdf = new FPDF();     $pdf->AddPage();     $pdf->SetFont('Arial','B',16);     $pdf->Cell(40,10,'Hello World!');     $pdf->Output();     ob_end_flush();  ?>