XXXVIII. 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.

The general idea of FDF is similar to HTML forms. The difference 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 which 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 documentation 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..


You need the FDF toolkit SDK available from As of PHP 4.3 you need at least SDK version 5.0. The FDF toolkit library is available in binary form only, platforms supported by Adobe are Win32, Linux, Solaris and AIX.


You must compile PHP with --with-fdftk[=DIR].

注: 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. The configure script supports both the directory structure of the FDF SDK distribution and the usual DIR/include / DIR/lib layout, so you can point it either directly to the unpacked distribution directory or put the header file and the appropriate library for your platform into e.g. /usr/local/include and /usr/local/lib and configure with --with-fdftk=/usr/local.

Note to Win32 Users: In order to enable this module on a Windows environment, you must copy fdftk.dll from the DLL folder of the PHP/Win32 binary package to the SYSTEM32 folder of your windows machine. (Ex: C:\WINNT\SYSTEM32 or C:\WINDOWS\SYSTEM32)


本扩展模块在 php.ini 中未定义任何配置选项。



Most fdf functions require a fdf resource as their first parameter. A fdf resource is a handle to an opened fdf file. fdf resources may be obtained using fdf_create(), fdf_open() and fdf_open_string().


以下常量由本扩展模块定义,因此只有在本扩展模块被编译到 PHP 中,或者在运行时被动态加载后才有效。

FDFValue (integer)

FDFStatus (integer)

FDFFile (integer)

FDFID (integer)

FDFFf (integer)

FDFSetFf (integer)

FDFClearFf (integer)

FDFFlags (integer)

FDFSetF (integer)

FDFClrF (integer)

FDFAP (integer)

FDFAS (integer)

FDFAction (integer)

FDFAA (integer)

FDFAPRef (integer)

FDFIF (integer)

FDFEnter (integer)

FDFExit (integer)

FDFDown (integer)

FDFUp (integer)

FDFFormat (integer)

FDFValidate (integer)

FDFKeystroke (integer)

FDFCalculate (integer)

FDFNormalAP (integer)

FDFRolloverAP (integer)

FDFDownAP (integer)


The following examples shows just the evaluation of form data.

例子 1. Evaluating a FDF document

// Open fdf from input string provided by the extension
// The pdf form contained several input text fields with the names
// volume, date, comment, publisher, preparer, and two checkboxes
// show_publisher and show_preparer.
$fdf = fdf_open_string($HTTP_FDF_DATA);
$volume = fdf_get_value($fdf, "volume");
"The volume field has the value '<b>$volume</b>'<br />";

$date = fdf_get_value($fdf, "date");
"The date field has the value '<b>$date</b>'<br />";

$comment = fdf_get_value($fdf, "comment");
"The comment field has the value '<b>$comment</b>'<br />";

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

if (
fdf_get_value($fdf, "show_preparer") == "On") {
$preparer = fdf_get_value($fdf, "preparer");
"The preparer field has the value '<b>$preparer</b>'<br />";
} else
"Preparer shall not be shown.<br />";

fdf_add_doc_javascript -- Adds javascript code to the FDF document
fdf_add_template -- Adds a template into the FDF document
fdf_close -- Close an FDF document
fdf_create -- Create a new FDF document
fdf_enum_values -- Call a user defined function for each document value
fdf_errno -- Return error code for last fdf operation
fdf_error -- Return error description for fdf error code
fdf_get_ap -- Get the appearance of a field
fdf_get_attachment -- Extracts uploaded file embedded in the FDF
fdf_get_encoding -- Get the value of the /Encoding key
fdf_get_file -- Get the value of the /F key
fdf_get_flags -- Gets the flags of a field
fdf_get_opt -- Gets a value from the opt array of a field
fdf_get_status -- Get the value of the /STATUS key
fdf_get_value -- Get the value of a field
fdf_get_version -- Gets version number for FDF API or file
fdf_header -- Sets FDF-specific output headers
fdf_next_field_name -- Get the next field name
fdf_open_string -- Read a FDF document from a string
fdf_open -- Open a FDF document
fdf_remove_item -- Sets target frame for form
fdf_save_string -- Returns the FDF document as a string
fdf_save -- Save a FDF document
fdf_set_ap -- Set the appearance of a field
fdf_set_encoding -- Sets FDF character encoding
fdf_set_file -- Set PDF document to display FDF data in
fdf_set_flags -- Sets a flag of a field
fdf_set_javascript_action -- Sets an javascript action of a field
fdf_set_on_import_javascript -- Adds javascript code to be executed when Acrobat opens the FDF
fdf_set_opt -- Sets an option of a field
fdf_set_status -- Set the value of the /STATUS key
fdf_set_submit_form_action -- Sets a submit form action of a field
fdf_set_target_frame -- Set target frame for form display
fdf_set_value -- Set the value of a field
fdf_set_version -- Sets version number for a FDF file

add a note add a note User Contributed Notes
wesley_grant at yahoo dot com
12-Jan-2006 07:37
Changing the


directive in the php.ini file to 'private'

seems to resolve the issue with sending fdf data and session headers at the same time to Internet Explorer.
bmount at livid dot us
19-Oct-2005 11:05
For those of you struggling with FDF in Internet Explorer, here is your solution:


This will fix the page not found error.
04-May-2005 04:08
Use "Yes" instead of "On" to populate checkboxes.
08-Mar-2005 09:56
For the example below, I have not b een able to have it populate checkbox fields.
g8z at yahoo dot com
18-Oct-2004 02:46
This is for users who are looking for a way to merge HTML form data with a PDF Form, then output the PDF Form with data populated in it, to a web browser.

This is a pure PHP solution which does NOT require the FDF toolkit. Contributed by


// the full http path to the PDF form
$form = '';

create_fdf ($pdffile, $strings, $keys)
$fdf = "%FDF-1.2\n%\n";
$fdf .= "1 0 obj \n<< /FDF << /Fields [\n";

   foreach (
$strings as $key => $value)
$key = addcslashes($key, "\n\r\t\\()");
$value = addcslashes($value, "\n\r\t\\()");
$fdf .= "<< /T ($key) /V ($value) >> \n";
   foreach (
$keys as $key => $value)
$key = addcslashes($key, "\n\r\t\\()");
$fdf .= "<< /T ($key) /V /$value >> \n";

$fdf .= "]\n/F ($pdffile) >>";
$fdf .= ">>\nendobj\ntrailer\n<<\n";
$fdf .= "/Root 1 0 R \n\n>>\n";
$fdf .= "%%EOF";


// Fill in text fields
$strings = array(
'date' => '10/17/2004',
'full_name' => 'Joe Doe',
'phone_num' => '123-4567',
'company' => 'ACME Widgets',
'amount' => 'USD 100.00'

// Fill in check boxes/radio buttons
$keys = array('
=> 'male',//radio button
'is_adult' => 'Off',//checkbox
'urgent' => 'On'//checkbox

// Output the PDF form, with form data filled-in
header('Content-type: application/vnd.fdf');
create_fdf($form, $strings, $keys);

sid at accesspdf dot com
08-Oct-2004 02:09
Basic FDF data is easy to create using native PHP; you don't need Adobe's FDF Toolkit. I wrote a function for this purpose called forge_fdf(). You can download it from:

I created it for my book, PDF Hacks. An example of forge_fdf() in action can be viewed online:

Download the full code for this online example from:

Note how the PDF form data is submitted back to the server via POST rather than FDF. No need to parse FDF.


Sid Steward
ronsantiago at hotmail dot com
03-Oct-2004 12:18
Use these functions instead if you want to create an FDF file without installing the FDF toolkit. You would use it the same way as the fdf_* functions. BTW, I only wrote the basic library functions for creating FDFs.

define('ntk_FDFValue', 0);
define('ntk_FDFStatus', 1);
define('ntk_FDFFile', 2);
define('ntk_FDFID',    3);
define('ntk_FDFFf',    5);
define('ntk_FDFSetFf', 6);
define('ntk_FDFClearFf', 7);
define('ntk_FDFFlags', 8);
define('ntk_FDFSetF', 9);
define('ntk_FDFClrF',    10);
define('ntk_FDFAP',    11);
define('ntk_FDFAS',    12);
define('ntk_FDFAction',    13);
define('ntk_FDFAA',    14);
define('ntk_FDFAPRef', 15);
define('ntk_FDFIF',    16);
define('ntk_FDFEnter', 0);
define('ntk_FDFExit',    1);
define('ntk_FDFDown',    2);
define('ntk_FDFUp',    3);
define('ntk_FDFFormat',    4);
define('ntk_FDFValidate',    5);
define('ntk_FDFKeystroke', 6);
define('ntk_FDFCalculate', 7);
define('ntk_FDFNormalAP',    1);
define('ntk_FDFRolloverAP',    2);
define('ntk_FDFDownAP',    3);

function ntk_fdf_header() {
  header('Content-type: application/vnd.fdf');

function ntk_fdf_create() {
  $fdf['header'] = "%FDF-1.2\n%\n1 0 obj \n<< /FDF ";
  $fdf['trailer'] = ">>\nendobj\ntrailer\n<<\n/Root 1 0 R \n\n>>\n%%EOF";
  return $fdf;

function ntk_fdf_close(&$fdf) {

function ntk_fdf_set_file(&$fdf, $pdfFile) {
  $fdf['file'] = $pdfFile;

function ntk_fdf_set_target_frame(&$fdf, $target) {
  $fdf['target'] = $target;

function ntk_fdf_set_value(&$fdf, $fieldName, $fieldValue) {
  $fdf['values'] = array_merge($fdf['values'], array($fieldName => $fieldValue));

function ntk_fdf_add_doc_javascript(&$fdf, $scriptName, $script) {
  $fdf['docscripts'] = array_merge($fdf['docscripts'], array($scriptName => $script));

function ntk_fdf_set_javascript_action(&$fdf, $fieldName, $trigger, $script) {
  $fdf['fieldscripts'] = array_merge($fdf['fieldscripts'], array($fieldName => array($script, $trigger)));

function ntk_fdf_save(&$fdf, $fdfFile = null) {
  $search = array('\\', '(', ')');
  $replace = array('\\\\', '\(', '\)');
  $fdfStr = $fdf['header'];
  $fdfStr.= "<< ";
  if(isset($fdf['file'])) {
   $fdfStr.= "/F (".$fdf['file'].") ";
  if(isset($fdf['target'])) {
   $fdfStr.= "/Target (".$fdf['target'].") ";

  if(isset($fdf['docscripts'])) {
   $fdfStr.= "/JavaScript << /Doc [\n";
   // populate the doc level javascripts
   foreach($fdf['docscripts'] as $key => $value) {
     $fdfStr.= "(".str_replace($search, $replace, $key).")(".str_replace($search, $replace, $value).")";
   $fdfStr.= "\n] >>\n";

  if(isset($fdf['values']) || isset($fdf['fieldscripts'])) {
   // field level
   $fdfStr.= "/Fields [\n";

   if(isset($fdf['fieldscripts'])) {
     // populate the field level javascripts
     foreach($fdf['fieldscripts'] as $key => $val) {
       $fdfStr .= "<< /A << /S /JavaScript /JS (".str_replace($search, $replace, $val[0]).") >> /T (".str_replace($search, $replace, $key).") >>\n";
   if(isset($fdf['values'])) {
     // populate the fields
     foreach($fdf['values'] as $key => $value) {
       $fdfStr .= "<< /V (".str_replace($search, $replace, $value).") /T (".str_replace($search, $replace, $key).") >>\n";

   $fdfStr.= "]\n";
  $fdfStr.= ">>";
  $fdfStr.= $fdf['trailer'];

  if($fdfFile) {
   $handle = fopen($fdfFile, 'w');
   fwrite($handle, $fdfStr);
  else {
   echo $fdfStr;
m1tk4 at hotmail dot com
01-Jul-2004 01:34
If you want to add FDF support without rebuilding your RedHat EL3 / Fedora PHP RPMs, see instructions at
software at yvanrodrigues dot com
26-Mar-2004 06:16
Do not use version 6 of the fdftk.dll (windows) with PHP4.3.4, use the one that comes with PHP.

If you use the newer DLL fdf_create will not return a valid handle.
fleischer at mail dot com
18-Dec-2003 11:40
The code suggested by greg@... and adam@... is extremely helpful, but I've found out (the hard way) that unclosed parentheses within strings contained in the input array ($values in greg's code or $pdf_data in adam's) will cause Acrobat to issue an error to the effect that the file is corrupted. In other words, if there are strings such as "a) my first point; b) my second point" in the input array, the resulting PDF/FDF file will be considered corrupted by Acrobat. This apparently happens because all the field names in the structure of an FDF file are enclosed in parentheses.

The solution I've devised is to escape all opening and closing parentheses with a backslash, which in turn means you need to escape all backslashes. The code below does all that.



function output_fdf ($pdf_file, $pdf_data)
   $fdf = "%FDF-1.2\n%\n";
   $fdf .= "1 0 obj \n<< /FDF ";
   $fdf .= "<< /Fields [\n";

   $search = array('\\', '(', ')');
   $replace = array('\\\\', '\(', '\)');
   foreach ($pdf_data as $key => $val)
       $clean_key = str_replace($search, $replace, $key);
       $clean_val = str_replace($search, $replace, $val);
       $fdf .= "<< /V ($clean_val)/T ($clean_key) >> \n";

   $fdf .= "]\n/F ($pdf_file) >>";
   $fdf .= ">>\nendobj\ntrailer\n<<\n";
   $fdf .= "/Root 1 0 R \n\n>>\n";
   $fdf .= "%%EOF";

   return $fdf;
mirage at rateaprof dot com
08-May-2003 08:33
If you get the new  fdftkv5.tar.gz  from adobe's site (per the link above), you'll get some totally new spacing and capitalization of files.  To make the current 4.3.1 configure, you need to do a few things.

untar fdftkv5.tar.gz into /usr/local
cd /usr/local
#for ease of use
ln -s FDFToolkit\ for\ UNIX fdf

cd fdf
ln -s Headers\ And\ Libraries HeadersAndLibraries

#may need to modify the following for your OS
ln -s LINUX linux
cd linux/C

cd ..
cd ..
ln -s Headers headers
cd headers
ln -s FDFTK.H fdftk.h

And that should get you going... and to whoever is maintaining the configure script, please be aware there are changes in the FDF Toolkit.
05-Mar-2003 10:17
Maybe you have to use Header-function that your browser will regonize xfdf-file. Like this:

Header( "Content-type: application/vnd.adobe.xfdf");
jeff at cowart dot net
20-Jan-2003 12:06
I have tried to use the scripts above by adam and Toppi and I have been unable to get them to work unless I save the generated fdf file and then open it manually in acrobat.
Toppi at i-Mehl dot De
27-Nov-2002 04:18
I tried a lot with FDF -> PDF and merging these documents...
in my opinon xfdf is more handy than fdf... for those who'd like to try: feel free to use this little function to generate an xfdf document from an array.


function array2xfdf($xfdf_data, $pdf_file) {
// Creates an XFDF File from a 2 dimensional
// Array Format: "array ("key1" => "content1", "key2" => "content2");
$xfdf = "<?xml version='1.0' encoding='UTF-8'?>\n";
$xfdf .= "<xfdf xmlns='' xml:space='preserve'>\n";
$xfdf .= "<fields>\n";
// Loop -> Array to XFDF Data
foreach ($xfdf_data as $key => $val) {
$xfdf .= "<field name='".$key."'>\n";
$xfdf .= "<value>".$val."</value>\n";
$xfdf .= "</field>\n";
// XFDF "Footer"
$xfdf .= "</fields>";
$xfdf .= "<f href='".$pdf_file."'/>";
$xfdf .= "</xfdf>";
return $xfdf;
mitka at
22-Oct-2002 07:24

If you handled the FDF POSTs via $HTTP_RAW_POST_DATA as in user contributed scripts above, it's good to know that once you decide to rebuild PHP with FDFToolkit support, $HTTP_RAW_POST_DATA will be undefined.

Good news - $HTTP_FDF_DATA _will_ be defined instead. (Look at the example above).To get the user contributed scripts working in both plain PHP and PHP+FDFToolkit use


where $HTTP_RAW_POST_DATA mentioned.

Dimitri Tarassenko
adam at andemyte dot com
03-Aug-2002 02:30
Here is yet another example of generating pre-filled PDFs without using the FDF functions. This function takes two args: a URL to the PDF (like "" and an array with all the field's values.

   any content is spooled to the browser, or the function will fail!
   void output_fdf (string $pdf_file, array $pdf_data)

       $pdf_file:  a string containing a URL path to a PDF file on the
                   server. This PDF MUST exist and contain fields with
                   the names referenced by $pdf_data for this function
                   to work.
       $pdf_data:  an array of any fields in $pdf_file that you want to
                   populate, of the form key=>val; where the field
                   name is the key, and the field's value is in val.

function output_fdf ($pdf_file, $pdf_data) {
   $fdf = "%FDF-1.2\n%\n";
   $fdf .= "1 0 obj \n<< /FDF ";
   $fdf .= "<< /Fields [\n";
   foreach ($pdf_data as $key => $val)
       $fdf .= "<< /V ($val)/T ($key) >> \n";
   $fdf .= "]\n/F ($pdf_file) >>";
   $fdf .= ">>\nendobj\ntrailer\n<<\n";
   $fdf .= "/Root 1 0 R \n\n>>\n";
   $fdf .= "%%EOF";
   /* Now we display the FDF data which causes Acrobat to start  */
   header ("Content-Type: application/vnd.fdf");
   print $fdf;
noah at NOSPAMbrandfidelity dot com
09-Mar-2002 12:26
function parse($file) {
               if (!preg_match_all("/<<\s*\/V([^>]*)>>/x",
               for ($i=0;$i<count($out);$i++) {
                       $pattern = "<<.*/V\s*(.*)\s*/T\s*(.*)\s*>>";
                       $thing = $out[$i][1];
                       if (eregi($pattern,$out[$i][0],$regs)) {
                               $key = $regs[2];
                               $val = $regs[1];
                               $key = preg_replace("/^\s*\(/","",$key);
                               $key = preg_replace("/\)$/","",$key);
                               $key = preg_replace("/\\\/","",$key);
                               $val = preg_replace("/^\s*\(/","",$val);
                               $val = preg_replace("/\)$/","",$val);
                               $matches[$key] = $val;
               return $matches;
gregDELETETHIS at laundrymat dot tv
22-Dec-2001 07:06
Here is an easy script to output fdf data to the browser without using the fdf toolkit or creating an actual fdf file on the server.
By the way acrobat is very picky about line breaks so you must leave the "\n" in the script. The script reads the variables posted to it from a form use POST and creates a fdf file from them. The field names posted to this script must match the field names in the pdf. Acrobat will ignore any that don't match.


//path to pdf file


$fdfdata = "%FDF-1.2\n%\n";
$fdfdata .= "1 0 obj \n<< /FDF ";
$fdfdata .= "<< /Fields [\n";

//loop that adds the field names and values
foreach($values as $key=>$val)
$fdfdata.="<< /V ($val)/T ($key) >> ";

$fdfdata .= "]\n";
$fdfdata .= "/F ($url) >>";
$fdfdata .= ">>\nendobj\ntrailer\n<<\n/Root 1 0 R\n>>\n";
$fdfdata .= "%%EOF";

/*** Now we display the FDF data which causes Acrobat to start  ***/

header ("Content-Type: application/vnd.fdf");


You can use javascript in the pdf to read the values from a GET method posted directly to the pdf. you can see both methods here:
joe at koontz dot net
29-Apr-2000 07:42
The simplest thing to do is get the FDF data from $HTTP_RAW_POST_DATA.  (unless you have the server library installed none of the fdf data gets parsed!) This is typical of  what you get:
1 0 obj
/FDF << /Fields [ << /V (0)/T (amount0)>> << /V (0)/T (amount1)>> << /V (0)/T (amount2)>>
<< /V (0)/T (amount3)>> << /V (0)/T (amount4)>> << /V (0)/T (amount5)>>
<< /V (0)/T (amount6)>> << /V (0)/T (amount7)>> << /V (0)/T (amount8)>>
<< /V (0)/T (amount9)>> << /V /0102 /T (chase_bk)>> << /V (0)/T (count)>>
<< /V (0)/T (invtotal)>> << /V (12/21/2000)/T (sent_ap)>> << /V /Off /T (spec_hand)>>
<< /V (041232)/T (transit_no)>> << /V (THIS FORM IS NOT COMPLETE!!!)/T (X)>>
/F (>>
/Root 1 0 R

kill everything before the [ and then parse it down into key value pairs. 
I wrote this to create an FDF, make sure you do a
header("Content-type: application/vnd.fdf");
before you echo the returned value to the user.
function FDFput(,$FDFpage)
 $A = "%FDF-1.2\n1 0 obj\n<< \n/FDF << /Fields [ \n";
 $C = " ] \n"    ;
     if ($FDFpage>"" ) {$C .=" /F ($FDFpage)>>\n";}
   $C .= ">>\n>> \nendobj\ntrailer\n\n<</Root 1 0 R>>\n%%EOF\n";
   $B = "";
 while (list($key, $val) = each($FDFData))
  if (strlen(trim($val)) > 0 && is_string($key))
   $B .= "<</T ($key) /V (". $val . ")>>\n";
//echo    "<</T ($key) /V (". $val . ")>>\n";
   return $A.$B.$C;
It ain't perfect - but it works. (I use HTML for posting to the server, FDF to the browser)