oop - 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;