FDF to PDF using PHP

Question

I was trying to create a pdf from an FDF file. I have created the FDF file succesfully. But when i try to convert it into pdf i get some errors. Below is the part of my code. the test.pdf file open in a download box and when i try to open it gives error "couldn't open test.pdf because it is either not supported file type or has been damaged"

if($fp=fopen($fdf_file,'w')){
            fwrite($fp,$fdf_data,strlen($fdf_data));
            echo $fdf_file,' written successfully.';
   header('Content-type: application/pdf');
   header('Content-Disposition: attachment; filename="test.pdf"');
   passssthru("pdftk test.pdf fill_form test.fdf output - ");
   exit;

        }else{
            die('U

Answer 1

Remove echo $fdf_file,' written successfully.';

Answer 2

To further debug this, check the size of the downloaded file, and take a peek at it in an editor. I am guessing you have output before or after this code.