Is there anyone who could help me?

Hiyas I'm not sure my last message was received, so I'll send my question once again: Well, I'm working on a webmailer-system (a php3-based pop3-client) that can and will be used by different users from the machine it's running on and I was wondering if there was any way to do something like an 'su', changing the user the script is executed under to the user currently logged in by the script. Reason: I'd like to give users the ability to save their options and preferences for the mailer and data for other mail-accounts. I'd like to accomplish this with a file in the users homedir, something like the usual .something config files, chowned to the logged in user and set to his/ her permissions... Can somebody help me? Ciao Tobias Schweitzer