OpenTBS is a plug-in for the TinyButStrong Template Engine.

TinyButStrong is a PHP Template Engine which has special template syntax and allows you to design templates in their natural editing tools. But it normally works only for Text files, including XML and HTML.

With TinyButStrong and its plug-in OpenTBS, you can use the template engine to merge OpenOffice documents and Ms Office documents with lot of facilities. All OpenDocument Format (ODF) and Office Open XML (OOXML) can be merged with OpenTBS, and also XPS files (XPS is a PDF competitor provided by Microsoft). In fact, all zip archives containing Xml/Html/Text files can be merged with OpenTBS.
What is special to OpenTBS:

Design your templates directly with OpenOffice or MS Office.
No exe file needed to merge documents.
No temporary files needed to merge documents.
Output directly as an http download, a new file on the disk, or as a string (for file attachment for example).
Works with both PHP 4 and PHP 5.
No PHP extension is required (If the Zlib extension is enabled it becomes easier to use templates, see more detail below)

You should know Template Engines and more specifically TinyButStrong to use OpenTBS.

OpenOffice.org Android viewer