sessions and global register

Hi I've been learning to get through sessions as it appears to be the hardest part of PHP I've come across. I found that includes must be stated underneath that of a session_start() for example otherwise a warning will appear that it can't start a session because a header has already been sent (or something to that effect). But a new warning has arose where it is suggesting something, but please note that the code actually executed okay. So, I want to clarify it's meaning and is it safe to just turn of the warning(session.bug_compat_warn ) and do nothing else? (I'm using v 4.3) Warning: Unknown(): Your script possibly relies on a session side-effect which existed until PHP 4.2.3. Please be advised that the session extension does not consider global variables as a source of data, unless register_globals is enabled. You can disable this functionality and this warning by setting session.bug_compat_42 or session.bug_compat_warn to off, respectively. in Unknown on line 0 Regards, Pat