Launching off from this previous post on the Stubbles Blog, two more posts (from two other developers) have been posted on the same subject:

• In this new post, Frank Kleine takes things a step further and talks about the same kind of type hinting but for more types - including arrays and objects. Examples of how he'd expect things to work followed.
• The other post is from Stephan Schmidt again and varies slightly off into the world of Namespaces to be included in PHP6 along with the use of annotations.

Stephan Schmidt has posted some thoughts about type hinting in PHP5 (what's there) and the same kind of functionality for objects in PHP6 (what's to come).

I was very pleased, that PHP 5 introduced type hints, although they are not available for primitives like string, int, boolean, etc. Still, I'd like to see the object type hint introduced in any future version of PHP that allows me to specify, that a method or function only accepts an object, regardless of the type of the object.

He gives the example of Java's handling of the functionality and what PHP does with the same type of code. He also mentions that, via the Reflection API extension, some of this is possible already, so why not just include it from here on out?