The website i'm working on unfortunately runs on PHP 5.1.6 so solutions which require a more up-to-date version are not feasible at the moment.

What I want to do is obtain the true file mime type.
I have a png on my desktop which is actually a PDF with a changed extension. The file gets past the mime validation due to the mime value of $_FILES[], however when png related functionality starts it work, it obviously throws errors as the file is not a valid png file.

What can I do to obtain the actual mime type of the file?