我无法使用pdftk-php填写PDF表单

I've created a PDF with form-fields. Now i want to fill out the PDF formular in PHP. I've tried pdftk-php, but when its return the PDF it's damaged. What to do? It will be good with some examples :)

require('pdf/pdftk-class.php');

    $pdfmaker = new pdftk_php;

    $fields_hidden = array(); 
    $fdf_data_strings= array("co_navn" => "test");
    $fields_readonly = array(); 

    $pdf_filename = "test.pdf";
    $fdf_data_names = array();
    $pdf_original = "Indberetningsskema.pdf";
    $pdfmaker->make_pdf($fdf_data_strings, $fdf_data_names, $fields_hidden, $fields_readonly, $pdf_original, $pdf_filename);

// Thomas Bolander