On the internals mailing list Anthony Ferrara posted a plea for unity on scalar types. If you want to know why it's so difficult to add scalar type hints to PHP, you should read it.

Scalar types are a hard problem. Not technically, but politically, because so many people use PHP in different ways. And everyone thinks their way is "the one true way".

http://news.php.net/php.internals/84689

The RFC needs a 2/3 majority to pass. The yes-camp currently has 67%. Personally I really hope this proposal will get accepted.