"How can I use existing PDF documents as templates in PHP scripts?" is an FAQ. Apart from primitive and risky (I guess) string replacement, I haven't heard of any reasonable approach until Oliver of FPDF announced FPDI today. FPDI is an extension for FPDF which adds templating support based on PDF "Form XObjects" to the already amazing capabilites of the free pdf generator FPDF.

GOVERNOR. I have called you together, gentlemen, to
tell you an unpleasant piece of news. An Inspector-General
is coming.

Thursday we went to see The Inspector-General (Der Revisor) by Nikolai Vasilievich Gogol at the 25. Zürcher Theater Spektakel. It was performed by the Lithuanian theater company of award-winning director Alvis Hermanis. It was very Soviet, and intentionally, even provokingly, extremely old-fashioned, direct and straightforward. In an interview Hermanis made his case and explained that after all those "postmodernist" disturbance and perversions, on-stage brutality, nudity et cetera, the only way to be avant-garde these days was to make theater as it used to be, simple and uncooked: extremely normal theater. Actually this was an amazing experience, I -and I guess most of the public- kept feeling strangely alienated by this classic Russian comedy, which is so inherently Russian that the director said he was fairly surprised how an audience of foreigners with a cultural background so different could actually like it as much as it did. He found a nice picture for this situation saying it must "feel like sex with two condoms". And as the entire play was spoken in Lithuanian, the German-speaking audience wore wireless earplugs and listening to both the actors' text and a simultaneous translation, he even called it "telephone sex with two condoms". :)
You can listen to parts of that interview (mostly in German) at DRS2.
If you want to see this amazing inspector-general: They play it a third and last time this Saturday evening.