README

PHP PDF form filling library — actively maintained fork of tmw/fpdm (original script by Olivier Plathey, 2017).

Maintained by Five Quantum Bits — github.com/x5qubits/fpdm.

Why this fork?

The upstream repository has been unmaintained since 2019. Several critical issues were discovered while using it in production with real-world PDF templates (Romanian government forms):

• Checkboxes were invisible in Adobe Acrobat / Adobe Reader (worked in browsers and Foxit, not Adobe)
• PDFs with nested form fields (/Parent hierarchies) were only partially readable — 67 of 195 fields visible
• create_function() crashes on PHP 8.0+ (removed from the language)
• Empty string input in _bin2hex() caused fatal errors in PHP 8

Changes vs tmw/fpdm

1. Adobe Reader checkbox fix (critical)

Problem: The original set_field_checkbox() only wrote /AS /StateName (the appearance stream selector). Adobe Reader ignores /AS and reads /V (the field value) as authoritative. Result: checkboxes appeared checked in Chrome PDF viewer and Foxit but were always unchecked in Adobe.

Fix: After writing /AS, the library now also writes /V /StateName on the same widget object. If the template has no /V entry at all (common in ONRC templates), it is injected inline — without inserting new array elements which would corrupt xref offsets.

Before: /AS /Yes          ← Adobe ignores this
After:  /AS /Yes\n/V /Yes ← Adobe reads /V ✓

2. Nested field support via /Parent chain (major)

Problem: Complex PDF templates use AcroForm field hierarchies — a parent field contains children, children can have grandchildren, etc. Field names in such PDFs look like clasa_caen.0.3 or sectiune.row.col. The original parser only saw top-level objects and missed all nested widgets.

Fix: After the main parse loop, the library now:

1. Captures /Parent object references during parsing
2. Stores nested widgets under temporary __obj_X keys
3. Post-processes to walk each /Parent chain and rebuild full dotted paths
4. Replaces temp keys with final paths like clasa_caen.0.3

Result: a Romanian ONRC Declaratie Anexa 4 template went from 67 accessible fields to 195.

3. PHP 8.0+ compatibility (breaking in original)

create_function() removed in PHP 8.0 The _set_field_value() method used create_function() to build a callback dynamically. This was deprecated in PHP 7.2 and removed in PHP 8.0 — causing a fatal error on any PHP 8 server. Fixed by replacing it with a proper closure using use ($self, $value).

_bin2hex() crash on empty string The function used a do...while loop which unconditionally accessed $str[0] before checking length. On an empty string this triggers a warning in PHP 7 and a fatal error in PHP 8. Fixed with an early return guard and a for loop.

Installation

composer require x5qubits/fpdm

Or standalone:

require_once '/path/to/src/fpdm.php';

Usage

Basic — fill text fields

$fields = [
    'name'    => 'Ion Popescu',
    'address' => 'Str. Victoriei nr. 10',
    'date'    => '17.04.2026',
];

$pdf = new FPDM('template.pdf');
$pdf->Load($fields, true); // true = UTF-8
$pdf->Merge();
$pdf->Output(); // stream to browser

Checkboxes (Adobe Reader compatible)

$pdf = new FPDM('template.pdf');
$pdf->useCheckboxParser = true; // required

$pdf->Load([
    'agree_terms' => true,   // checked
    'newsletter'  => false,  // unchecked
    'type_srl'    => true,
    'type_pfa'    => false,
], true);

$pdf->Merge();
$pdf->Output('F', 'output.pdf'); // F = save to file

You do not need to know the internal checkbox state name (Yes, On, 31.5, etc.) — it is read from the template automatically.

Nested / hierarchical fields

// Fields like "clasa_caen.0.3" work out of the box
$fields = [];
foreach (['6201', '6202', '6311'] as $i => $code) {
    $fields["clasa_caen.0.$i"]      = $code;
    $fields["clasa_caen_desc.0.$i"] = 'Software development';
}

$pdf = new FPDM('template_with_nested_fields.pdf');
$pdf->useCheckboxParser = true;
$pdf->Load($fields, true);
$pdf->Merge();
$pdf->Output('F', 'output.pdf');

Template compatibility

If your PDF throws an error about object streams or incremental updates, run it through ilovepdf.com/repair-pdf first. The repaired file is typically smaller and fully compatible.

Pattern for trying multiple candidates:

foreach (['template_repaired.pdf', 'template.pdf'] as $tpl) {
    try {
        $pdf = new FPDM($tpl);
        $pdf->useCheckboxParser = true;
        $pdf->Load($fields, true);
        $pdf->Merge();
        $pdf->Output('F', 'output.pdf');
        break;
    } catch (Exception $e) {
        $lastError = $e->getMessage();
    }
}

Output modes

Requirements

• PHP 7.4 or higher (PHP 8.0, 8.1, 8.2, 8.3 supported)
• No other dependencies

Credits

• Olivier Plathey — original FPDM script (fpdf.org)
• codeshell — tmw/fpdm Composer package and PHP 7 compatibility
• Five Quantum Bits — this fork (fiveqb.com)