I'm Wondering What Design Pattern The Yii Component Object's Behavior Implements.

The missing method is delegated though __call to behavioral object registered to the components.

Is it a delegation pattern or something? I’d like to learn about the more formal pattern name.

See THE DEFINITIVE GUIDE TO YII: Fundamentals/Component - 3. Component Behavior.

Personnally I would not qualify behaviors as mixins, but rather as visitors (http://sourcemaking.com/design_patterns/visitor ) as the behavior is handed a reference to the visited class. A mixin would have at least have acces to protected members of the class it refers to.

PHP traits are closer to mixins than Yii’s behaviors.

It is however - IMHO - not really either.

Also, behaviors attache themselves to events which is again IMHO neither in a visitor nor a mixin.