I have a PHP web application (running on Apache/Linux) that, among other things, allows some browsing of local files on the web server. Since Apache is running as a special "www" user, PHP has access to everything that "www" can access, whichever user is logged into the application.
What is the best way to limit the access to files according to the Unix filesystem privileges for the logged-in user? Ideally, I could spawn off a new process with user ID being the logged in user, but I'm not sure if that's possible. Alternatively, is there a standard PHP library somewhere that will do the permission checking and access the files?