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.