Josh Adell has a new post today looking at the "powerful combination" of using traits and interfaces in PHP applications. He shows how, despite traits not implementing the interface directly, they can be used to make other classes adhere to them simply by "using" them.

If you're not using interfaces in PHP, you are missing out on a powerful object-oriented programming feature. An interface defines how to interact with a class. By defining an interface and then implementing it, you can guarantee a "contract" for consumers of a class. Interfaces can be used across unrelated classes. And they become even more useful when combined with the new traits feature in PHP 5.4.

He illustrates with a package shipping example and uses an "Addressable" Interface to define the structure for both a Company and Users class. He includes code showing how to implement it in a more traditional "implements" way in a class, but also shows an interesting way to achieve the same thing with traits. Having a trait that follows the interface makes it easy to have a class adhere to the interface just by including the trait (or "using" it).

In a new tutorial posted on the Zend Developer Zone today Steve Hollis looks at something several PHP developers have said they want to seen in the language - traits - and how, until then, you can use traits now (well, sort of).

So why do we need traits, anyway? PHP is a single inheritance language, meaning that each class can only extend one other. This allows us to build logical class hierarchies which extend functionality in a "vertical" way. [...] What we need is a means of re-using code other than simple inheritance. That's where traits come in. Traits are classes containing a collection of methods, usually relating to a particular behaviour.

He shares a way that you can mimic some of the functionality that traits would give you (full code is available here) with an abstract trait class, reflection and a "superclass" that's extended to pass off the requests to the correct child object.

On the Stubbles blog, Frank Kleine has pointed out a proposal from Stefan Marr to include functionality for traits in PHP.

As a language construct within PHP it would be very easy to do the same, but easier to learn and to use. Beside some keyword issues (the RFC uses "use" as keyword, but this will of course conflict with namespaces) I'm wondering what this will have an impact on reflection - the RFC stays unclear about this.

A trait is a free-floating chink of functionality that, instead of being confined to a class (or file) that has to be called on to use it, exists where the developer can use it from anywhere at any time. This helps solve some of the issues with single inheritance in PHP.