PHP type-hinting traits

php traits type-hinting
arik picture arik · Jan 4, 2013 · Viewed 10.7k times · Source

I have a trait. For the sake of creativity, let's call this trait Trait:

trait Trait{    
    static function treat($instance){    
        // treat that trait instance with care
    }
}

Now, I also have a class that uses this trait, User. When trying to call treat with an instance of User, everything works. But I would like to type-hint that only instances of classes using Trait should be given as arguments, like that:

static function treat(Trait $instance){...}

Sadly, though, this results in a fatal error that says the function was expecting an instance of Trait, but an instance of User was given. That type of type-hinting works perfectly for inheritance and implementation, but how do I type-hint a trait?

Answer

Veda picture Veda · Jan 4, 2013

You can't as DaveRandom says. And you shouldn't. You probably want to implement an interface and typehint on that. You can then implement that interface using a trait.

Related questions

Traits vs. interfaces

I've been trying to study up on PHP lately, and I find myself getting hung up on traits. I understand the concept of horizontal code reuse and not wanting to necessarily inherit from an abstract class. What I don't understand …

Read More
How to override trait function and call it from the overridden function?

Scenario: trait A { function calc($v) { return $v+1; } } class MyClass { use A; function calc($v) { $v++; return A::calc($v); } } print (new MyClass())->calc(2); // should print 4 This code doesn't work, and I cannot find a way to call …

Read More
Traits in PHP – any real world examples/best practices?

Traits have been one of the biggest additions for PHP 5.4. I know the syntax and understand the idea behind traits, like horizontal code re-use for common stuff like logging, security, caching etc. However, I still don't know how I would …

Read More