add customization to README.md

Author: codeshell

README.md

@@ -1,45 +1,81 @@
-# Form filling
+# PDF Form Filling with FPDM
+
+## Package
+
 The FPDM class allows to fill out PDF forms, i.e. populate fields of a PDF file. It is **developed by Olivier Plathey**, author of the [FDPF Library](http://www.fpdf.org/), and has been released as [Skript 93](http://www.fpdf.org/en/script/script93.php).
 
 I created this repository for the following reasons:
+
 - make the current FPDM source available via [composer](https://packagist.org/packages/tmw/fpdm)
 - fix compatibility issues with PHP 7.x
-- bugfixing
+- bugfixing (changes to the original codebase are prefixed with `//FIX: change description` and ended with `//ENDFIX`)
+- add support for checkboxes (disabled by default, see customization to activate)
 
 This repository only contains the separate php class written for form filling. If you are looking for a repository containing the main FPDF Library, please head over to [github.com/Setasign/FPDF](https://github.com/Setasign/FPDF).
 
 Once again, all credits to Olivier Plathey for providing an easy to use extension to his FPDF library!
 
-# Version
+## Version
+
 Based on version 2.9 (2017-05-11) available from [fpdf.org/en/script/script93.php](http://www.fpdf.org/en/script/script93.php).
 
 Note: If you find that a new version has been hosted on fpdf.org, please do not hesitate to drop me [a short note](https://github.com/codeshell/fpdm/issues) to make sure I do not miss it out.
 
-# Usage
-## Composer (autoload)
-As this package specifies autoloading information, you can [autoload](https://getcomposer.org/doc/01-basic-usage.md#autoloading) all the dependencies by adding this to your code:
+## Usage
+
+### Composer (autoload)
+
+The preferred way of making FPDM available in your app is to install it via composer with
+
+`composer require tmw/fpdm`
+
+and then to [autoload](https://getcomposer.org/doc/01-basic-usage.md#autoloading) it by adding this to your code:
 
 `require 'vendor/autoload.php';`
 
-## Standalone Script
-Load the class file by calling
+### Standalone Script (legacy)
+
+Load the top level entry point by calling
 
 `require_once '/abolute/path/to/fpdm.php';`
 
 or
 
 `require_once './relative/path/to/fpdm.php';`
 
+## Customization
+
+Added support for checkboxes. The feature is not heavily tested but works for me. Can be enabled with
+
+```php
+<?php
+$fields = array(
+    'my_checkbox'    => 'anything that evaluates to true.', // checkbox will be checked;  Careful, that includes ANY non-empty string (even "no" or "unchecked")
+    'another_checkbox' => false, // checkbox will be UNchecked; empty string or 0 work as well
+);
+
+$pdf = new FPDM('template.pdf');
+$pdf->useCheckboxParser = true;
+$pdf->Load($fields, false); // second parameter: false if field values are in ISO-8859-1, true if UTF-8
+$pdf->Merge();
+$pdf->Output();
+```
+
+You don't have to figure out the technical names of checkbox states. They are retrieved during the parsing process.
+
+## Original Info Page
+
+### Information
 
-# Original Info Page
-## Information
 Author: Olivier
 
 License: FPDF
 
-## Description
+### Description
+
 This script allows to merge data into a PDF form. Given a template PDF with text fields, it's
 possible to inject values in two different ways:
+
 - from a PHP array
 - from an <abbr title="Forms Data Format">FDF</abbr> file
 
@@ -49,10 +85,11 @@ Note: if your template PDF is not compatible with this script, you can process i
 [PDFtk](https://www.pdflabs.com/tools/pdftk-server/) this way:
 
 `pdftk modele.pdf output modele2.pdf`
-  
+
 Then try again with modele2.pdf.
 
-## Example
+### Example
+
 This example shows how to merge data from an array:
 
 ```php
@@ -76,4 +113,4 @@ $pdf->Output();
 ?>
 ```
 
-View the result [here](http://www.fpdf.org/en/script/ex93.pdf). 
+View the result [here](http://www.fpdf.org/en/script/ex93.pdf).