If you are really interested in PHP 6 and its Unicode support you should read:
http://www.zend.com/zend/week/php-unicode-design.txt
(and in general http://www.zend.com/zend/week/)
plus cvs/php6/README.UNICODE and cvs/php6/README.UNICODE-UPGRADES
After you compile PHP 6, make sure that you have enabled unicode_semantics = on in php.ini (an old PHP 5 configuration file will not do as it does not provide those new Unicode-related options).