(http://php.net/manual/en/language.oop5.traits.php#language.oop5.traits)
As of PHP 5.4.0, PHP implements a method of code reuse called Traits.
Traits are a mechanism for code reuse in single inheritance languages such as PHP. A Trait is intended to reduce some limitations of single inheritance by enabling a developer to reuse sets of methods freely in several independent classes living in different class hierarchies. The semantics of the combination of Traits and classes is defined in a way which reduces complexity, and avoids the typical problems associated with multiple inheritance and Mixins.
A Trait is similar to a class, but only intended to group functionality in a fine-grained and consistent way. It is not possible to instantiate a Trait on its own. It is an addition to traditional inheritance and enables horizontal composition of behavior; that is, the application of class members without requiring inheritance.
Example #1 Trait example
<?php
trait ezcReflectionReturnInfo {
function getReturnType() { /*1*/ }
function getReturnDescription() { /*2*/ }}
class ezcReflectionMethod extends ReflectionMethod {
use ezcReflectionReturnInfo; /* ... */}
class ezcReflectionFunction extends ReflectionFunction {
use ezcReflectionReturnInfo; /* ... */}
?>
Precedence ¶
An inherited member from a base class is overridden by a member inserted by a Trait. The precedence order is that members from the current class override Trait methods, which in turn override inherited methods.
Example #2 Precedence Order Example
An inherited method from a base class is overridden by the method inserted into MyHelloWorld from the SayWorld Trait. The behavior is the same for methods defined in the MyHelloWorld class. The precedence order is that methods from the current class override Trait methods, which in turn override methods from the base class.
<?phpclass Base {
public function sayHello() { echo 'Hello '; }}
trait SayWorld {
public function sayHello() {
parent::sayHello(); echo 'World!'; }}
class MyHelloWorld extends Base {
use SayWorld;}$o = new MyHelloWorld();$o->sayHello();?>
