Actually I tried jerdo's suggestion of setting "register_globals=on" in PHP.ini. I had already tried this before without success. However when I first tried, I never rebooted Apache after making the change. Most of the directives in PHP.ini don't seam to require rebooting Apache to take affect but this one does.
Also, although I have written code in the past that expects the GET and POST variables to automatically be passed as golbals, I can understand why they have changed this behaviour in the new PHP version. Therefore all the code I write from now on will either explicitly import the variables I want or use the $HTTP_GET_VARS or $HTTP_POST_VARS arrays to access them.
Regards,
Alan