Sessions in PHP... where to start???

Hi everybody! I have a problem and I was told to check out the sessions part in PHP. What I want to deal with is the following : I have a PHP page with a form, where the user writes some data. These data are then written into a file which is then used in a system command as input for an external program (NOTE: The data MUST be written into a file, it cannot be done elsewhise, because the external program takes a file as input). The thing is that I must somehow create a file everytime a user enters data into the form, so I must learn something on sessions I think. My question is, since I don't have a login system or something like that, but just want to create a different file each time (with the session_id being part of it, so that the file is unique), which session commands do I need? --------------------------------- Yahoo! Mail Use Photomail to share photos without annoying attachments.