Session ID not getting propogated in the URL properly?

When you generate URLs yourself using the SID variable, it must come first in the URL parameter list.

Example:
If SID expands to "some_session=123" then this does NOT work:

somefile.php?var1=value&some_session=123

The SID must come first in the query string:

somefile.php?some_session=123&var1=value

If the SID does not come first in the query string then session_start() does not recognise the session variable in the URL and creates a NEW session instead of loading the old one.