Phpdocx use php4log to get info, no screen messages. When you download a file using header function, PHP can't write any message before downloading or you'll get a header error, so DOCX files are created in the specified path and you see a blank screen.
If you need to create and download the DOCX file, please use createDocxAndDownload method.
About '<?php but no ?>', please read the following text:
http://framework.zend.com/manual/en/coding-standard.php-file-formatting.html
Regards.