PHP traits - defining generic constants

Question

What is the best way to define constants that may be used by a number of classes within a namespace? I'm trying to avoid too much inheritance, so extending base classes is not an ideal solution, and I'm struggling to find a good solution using traits. Is this in any way possible in PHP 5.4 or should a different approach be taken?

I have the following situation:

trait Base {     // Generic functions }  class A  {     use Base; }  class B  {     use Base; } 

The problem is that it is not possible to define constants in PHP traits. Ideally, I would want something like the following:

trait Base {     const SOME_CONST = 'someconst';     const SOME_OTHER_CONST = 'someotherconst';      // Generic functions } 

Then these could be accessed though the class that applies the trait:

echo A::SOME_CONST; echo B::SOME_OTHER_CONST; 

But due to the limitations of traits this isn't possible. Any ideas?

Answer 1

I ended up using user sectus's suggestion of interfaces as it feels like the least-problematic way of handling this. Using an interface to store constants rather than API contracts has a bad smell about it though so maybe this issue is more about OO design than trait implementation.

interface Definition {     const SOME_CONST = 'someconst';     const SOME_OTHER_CONST = 'someotherconst'; }  trait Base {     // Generic functions }  class A implements Definition {     use Base; }  class B implements Definition {     use Base; } 

Which allows for:

A::SOME_CONST; B::SOME_CONST; 

Answer 2

You could also use static variables. They can be used in the class or the trait itself. - Works fine for me as a replacement for const.

trait myTrait {     static $someVarA = "my specific content";     static $someVarB = "my second specific content"; }  class myCustomClass {     use myTrait;      public function hello()     {         return self::$someVarA;     } }