In this new post to the PHP 10.0 blog today, Stas talks about duck typing, a method that lets the code decide the functionality to use rather than a direct relation to a parent.

Well, if you are into duck typing style of programming, it may be interesting for you to have an object that implements certain set of functions, but not necessary declares it at class definition. Languages like Smalltalk do it all day along, so why PHP couldn't?

His example defines an interface Cow and a class MooingGrassEater and a function, CowConsumer, that does the work. A classname is passed in and an instance of that class is checked with "implements" rather than "instanceof" to see if it uses the Cow interface. He points out a place where PHP itself uses something similar in user defined streams.

DevShed is continuing their "Enforcing Object Types in PHP" series with this new tutorial today. This time, they're focusing mor eon the use of the instanceof operator in PHP5.

This three-part series goes through the basic concepts of object type enforcement in PHP 4/PHP 5. It explores different approaches for checking types of objects to help you avoid possible code contamination when objects of incorrect type are inputted within PHP classes.

The end result of this article hopefully will help you to expand your grounding in how to implement object type enforcement in PHP 5, by developing some illustrative, object-oriented examples.

They start with a look at how not to do the object checking but provide a solution to the situation with the help of the instanceof operator. They explain its usage in the context of the widget class they've created, and show you how it can be integrated easily to simplify object validation.