How to implement server-sided applications that can process user's inputs?

Question

There are some web-based services such as converting .flv files into .mp3 files, .doc files into .pdf files, etc. These are the servers that take files from the user and apply respected applications (such as conversion). After that, the converted file may be available to the requested user.

I understand a little bit about writing a text and stores it into a server with javascript and php. What are the required tools and languages in order to achieve the above? Can some sort of C++ programs on the server side be invoked by some means? Or do I need completely different tools and methods?

Please provide me some keywords for this as I do not know what to google for.

Answer 1

You could write a simple php page that takes a user input via POST or GET that calls a server side executable and then, once the executable has done its thing, returns the results to the user as a http response.

Answer 2

Well for PDFs this can be done using entirely PHP. See http://www.php.net/manual/en/book.pdf.php for the PDF functions and http://uk.php.net/manual/en/pdf.examples-basic.php for some examples of usage.