PHP4 vs PHP5 - what's the (functional) difference(s)?

From: Ruby Tuesdays (NoSpamPlease_rubytuzdaiz_at_yahoo.com)
Date: 03/24/04 

Date: Wed, 24 Mar 2004 00:33:57 -0500

I had php script that used to work with PHP 4.3.4 but stop working as soon
as I use the PHP5RC1? Are there list differences that is deprecated/remove
from PHP4.3.4? Thanks