including files in PHP-pdf development

Hello, I am developing an application that ouputs the results of a database query to a PDF file using PHP. The only real problem I have encountered is in trying to use the "include" and/or "require" keywords. I have a block of code in another file that needs to called several times from my main PDF-generating PHP file. As of yet, the standard use of include or require doesn't seem to work: i.e. include 'output.inc'; Any ideas on what's going on or on how I might be able to introduce my code block multiple times into the main file? Thanks, Bill