Error about session

Hello, I have a problem with session.

I'm using Apache1.3.24 on Red Hat Linux7.2.
PHP Version 4.2.1.

If I write session_start() in my PHP script
it returns me Warning which says,

Warning: Failed to write session data (files).
Please verify that the current setting of
session.save_path is correct (/tmp)
in Unknown on line 0

But the directory /tmp can be written
also by "nobody", so I can't find out
what the problem is.

Would anyone help me?
I've been struggling with this a week(>_<)!

Try chmod'n that directory to 666 or 777 it sounds like PHP doesn't have the rights to write to that directory.

Thanks phil!

/tmp is 777.

How can I know that PHP doesn't have the
rights to write to that directory?
Or, how can I give PHP the rights?