Sorry, I left out an important detail. Chmod'ing to 770 won't do. If you want real security you NEED suexec/suphp. Otherwise the PHP scripts will run as Apache and be able to read everything, as well as write to any directory with 770 perms.
Clever users can bypass open_basedir restrictions:
This is banned
Code:
$data = file_get_contents('/path/to/another/users/file');But this isn't
Code:
$data = shell_exec('cat /path/to/another/users/file');
This, of course, can be banned using safe_mode configuration, but who knows if there's another hole, PHP being what it is.