Interaction on the WWW often means filling out forms, hitting the submit button and getting a certain result. HTML and HTTP provide a mechanism to perform this quite easily through forms. PHP has support for this mechanism in a very convenient way. The values of each input field are stored in PHP variables, with the same name as the input field.

A mechanism quite similar has been developed by Adobe, but for PDF documents. They simply call it Acrobat Forms. From the users point of view, the only difference in HTML forms and Acrobat forms is their appearance. The first one uses HTML documents, while the second one uses PDF documents to present the form.

For developers of web interfaces, Acrobat Forms can be handled like HTML forms, if the form provides its input data as HTML forms. However, Adobe has introduced a new format for form data called FDF (Form Data Format). PHP already includes support for this format.

The possibility to populate a PDF document with data, e.g. to customize it, is an additional feature of Acrobat Forms. . Using PDF documents as forms and populating PDF documents with data using PHP will be described in this article. Two examples demonstrate how easy it is.

Before you start trying the online examples in this article you should install the Acrobat Reader Plug-in or use Acrobat 4. If you want to test the PHP scripts on your own web server you will also need to install the FDF Toolkit and enable FDF support in PHP. Finally, if you want to develop your own PDF forms you will need Acrobat Exchange 3.x or Acrobat 4.