How to split a PHP class to separate files?

Question

I want to do something like class categories in Objective-C, to define a class in one file, implement some core methods there, then implement some helper methods in another without subclassing or interfaces, just "continue" the class.

Possible in PHP?

Answer 1

As of PHP 5.4, you can accomplish this with Traits. To quote the official documentation:

Traits [enable] a developer to reuse sets of methods freely in several independent classes living in different class hierarchies. [...] 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.

Using a trait allows you to store helper methods that address cross-cutting concerns in a central place and use these methods in whatever classes you need.

// File "HelperMethodTrait.php" trait HelperMethodTrait {     public function myIncredibleUsefulHelperFunction()     {         return 42;     } }  // File "MyClass.php" class MyClass {     use HelperMethodTrait;      public function myDomainSpecificFunction()     {         return "foobar";     } }  $instance = new MyClass(); $instance->myIncredibleUsefulHelperFunction(); // 42