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Forms Data Format functions

XXI. Forms Data Format functions

Forms Data Format (FDF) is a format for handling forms within PDF documents. You should read the documentation at for more information on what FDF is and how it is used in general.

Note: If you run into problems configuring php with fdftk support, check whether the header file FdfTk.h and the library are at the right place. They should be in fdftk-dir/include and fdftk-dir/lib. This will not be the case if you just unpack the FdfTk distribution.

The general idea of FDF is similar to HTML forms. The diffence is basically the format how data is transmitted to the server when the submit button is pressed (this is actually the Form Data Format) and the format of the form itself (which is the Portable Document Format, PDF). Processing the FDF data is one of the features provided by the fdf functions. But there is more. One may as well take an existing PDF form and populated the input fields with data without modifying the form itself. In such a case one would create a FDF document (fdf_create()) set the values of each input field (fdf_set_value()) and associate it with a PDF form (fdf_set_file()). Finally it has to be sent to the browser with MimeType application/vnd.fdf. The Acrobat reader plugin of your browser recognizes the MimeType, reads the associated PDF form and fills in the data from the FDF document.

If you look at an FDF-document with a text editor you will find a catalogue object with the name FDF. Such an object may contain a number of entries like Fields, F, Status etc.. The most commonly used entries are Fields whicht points to a list of input fields, and F which contains the filename of the PDF-document this data belongs to. Those entries are referred to in the FDF documention as /F-Key or /Status-Key. Modifying this entries is done by functions like fdf_set_file() and fdf_set_status(). Fields are modified with fdf_set_value(), fdf_set_opt() etc..

The following examples shows just the evaluation of form data.

Example 1. Evaluating a FDF document

// Save the FDF data into a temp file
$fdffp = fopen("test.fdf", "w");
fwrite($fdffp, $HTTP_FDF_DATA, strlen($HTTP_FDF_DATA));

// Open temp file and evaluate data
// The pdf form contained several input text fields with the names
// volume, date, comment, publisher, preparer, and two checkboxes
// show_publisher and show_preparer.
$fdf = fdf_open("test.fdf");
$volume = fdf_get_value($fdf, "volume");
echo "The volume field has the value '<B>$volume</B>'<BR>";

$date = fdf_get_value($fdf, "date");
echo "The date field has the value '<B>$date</B>'<BR>";

$comment = fdf_get_value($fdf, "comment");
echo "The comment field has the value '<B>$comment</B>'<BR>";

if(fdf_get_value($fdf, "show_publisher") == "On") {
  $publisher = fdf_get_value($fdf, "publisher");
  echo "The publisher field has the value '<B>$publisher</B>'<BR>";
} else
  echo "Publisher shall not be shown.<BR>";

if(fdf_get_value($fdf, "show_preparer") == "On") {
  $preparer = fdf_get_value($fdf, "preparer");
  echo "The preparer field has the value '<B>$preparer</B>'<BR>";
} else
  echo "Preparer shall not be shown.<BR>";
Table of Contents
fdf_open — Open a FDF document
fdf_close — Close an FDF document
fdf_create — Create a new FDF document
fdf_save — Save a FDF document
fdf_get_value — Get the value of a field
fdf_set_value — Set the value of a field
fdf_next_field_name — Get the next field name
fdf_set_ap — Set the appearance of a field
fdf_set_status — Set the value of the /STATUS key
fdf_get_status — Get the value of the /STATUS key
fdf_set_file — Set the value of the /F key
fdf_get_file — Get the value of the /F key
fdf_set_flags — Sets a flag of a field
fdf_set_opt — Sets an option of a field
fdf_set_submit_form_action — Sets an javascript action of a field
fdf_set_javascript_action — Sets an javascript action of a field

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