php4 Changelog: http://www.php.net/ChangeLog-4.php#4.3.10
php5 Changelog:http://www.php.net/ChangeLog-5.php#5.0.3
http://www.php.net
php5 Changelog:http://www.php.net/ChangeLog-5.php#5.0.3
These are maintenance releases that in addition to non-critical bug fixes address several very serious security issues.
http://www.php.net