Sameer Borate has a quick post to his blog today with some code that lets you read the version of a PDF document programmatically without a dependency on a PDF extension or library being installed.
The following [example] is a very short code to read the version number of a PDF document using PHP. I needed this recently during a PDF processing app developed in PHP. As Adobe uses different compression methods in various versions, it becomes necessary to be able to identify the version of the PDF under work.
The code opens the file with a fopen and parses a certain line for the major and minor version. The PDF extension for PHP can do something similar with the pdf_get_value function passing in either "major" or "minor" as the second parameter.