Does Safari handle PHP sessions differently than other browsers?

I have a test page with an example URL of:

This URL sets the tID and rID into a PHP session, before redirecting the user to another page to read the actual article if a login is not actually needed. The problem is that sometimes the Safari browser will correctly store everything in the session and other times it doesn’t. I can consistently duplicate this issue. Yet if I reload the page, suddenly the rest of the session variables are now showing up in the session. It seems to work fine in Chrome though, which is really strange.

Is there anything odd about Safari that I need to keep in mind when working with PHP sessions?