Just upgraded from PHP4.0.6 to PHP4.3; compatibility Warning

[MarkB423]

My host has just upgraded from PHP 4.0.6 to 4.3.1, and there is this warning at the bottom of my page:

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

Questions:

1) Is this just a general warning, or is there something wrong with my script? I could have sworn that I made everything compatible...

2) What would happen if the host turned session.bug_compat_42 from ON to OFF? (How would PHP perform differently?)

I know if he turned session.bug_compat_warn from ON to OFF, the message would go away, but PHP would perform the same.

Thank you!

[bsides2]

This may or may not be related to your problem. But our host also upgraded to 4.3.1 (without advanced warning mind you) and we experienced some very strange behaviour. After many days of debugging and hair pulling it turned out to be a very simple fix - make sure you register your session variables before giving them a value. Ie,

do this:
session_register('myVar');
$myVar = 'I am great';

and not this:
$myVar = 'I am great';
session_register('myVar');

HTH.

[MarkB423]

Was register_globals on or off?