Finding the "PDF Producer" or source application of a PDF

Is there a quick-and-dirty way to access the "producer" metadata of a PDF file, using Regex or XML parsing, from a PHP application?

The technique does not have to be infallible. The objective is to prompt the user if they upload a PDF created u开发者_如何学JAVAsing TeX.

You can hack the value out by looking for the producer or creator tag but it might be encoded rather than available as ascii.

On the command line, the following outputs a matching line:

 $ strings my.pdf | grep TeX


Producer (pdfTeX-1.40.10)
/Creator (TeX)
/PTEX.Fullbanner (This is pdfTeX, Version 3.1415926-1.40.10-2.2 (TeX Live 2009) kpathsea    version 5.0.0)

You might do something similar in PHP, see Read plain text from binary file with PHP.