Yeah, try http://www.tcpdf.org/

I used it a while back and found it pretty reasonable. Doesn't have deep dependencies on other pdf libraries, which is nice.

Php to pdf doesn't really make sense. What you want is the result of the interpretation of php code by some web server (which will be HTML most of the time, but can anything else) converted into pdf.

There exist a number of opensource solutions (http://www.xhtml2pdf.com/, http://code.google.com/p/wkhtmltopdf/ for example), and you can use solutions that convert to intermediary formats like postscript, djvu...

tcpdf mentioned by ChrisWaddle already looks more what you actually need though.