On the PHP in Action blog, there's a new post looking at a recent library that was posted to support type hinting on scalars. They agree with his choice of subjects, noting that they see type hinting as much more useful on scalars than on objects.

I admit that these judgments are hard to make. I could be wrong, more or less. Type hints are probably useful when code becomes stable enough and at the boundaries between modules. But I still tend to avoid using them until I get an actual bug that might have been prevented by a type hint. Their usefulness is and has to be an empirical question. The purpose of using them has to be catching errors earlier, so if they don't have that effect, there's no point.

He lists three reasons why he had given up on type hinting before, one being the limited usefulness when it came to objects. Applying it to scalars is a different matter, though, and can prevent improper passing of array/scalars when the other is needed.

DevShed has posted the last article in their "Enforcing Object Types in PHP" series today - "Using the Type Hinting Feature in PHP5".

[Returning] to the subject of this last tutorial, I'll introduce another method for enforcing object types in PHP 5: the "Type Hinting" feature. It can also be used in conjunction with the "instanceof" operator that you learned about before, in order to develop PHP applications that implement thorough routines for filtering unwanted objects. Generally speaking, when you finish reading this article, you should be armed with a few more methods for forcing object types in PHP, in this way expanding your overall knowledge of object-oriented programming.

They start with an introduction to type hinting and some basic examples of its use. From there, they build up a relevant example with the help of their (X)HTML widget class they've used throughout the series.