Conflict Resolution

Trying to use several traits into one class could result in issues involving conflicting methods. You need to resolve such conflicts manually.

For example, let’s create this hierarchy:

trait MeowTrait {
    public function say() {
        print "Meow \n";
    }
}

trait WoofTrait {
    public function say() {
        print "Woof \n";
    }
}

abstract class UnMuteAnimals {
    abstract function say();
}

class Dog extends UnMuteAnimals {
    use WoofTrait;
}

class Cat extends UnMuteAnimals {
    use MeowTrait;
}

Now, let’s try to create the following class:

class TalkingParrot extends UnMuteAnimals {
    use MeowTrait, WoofTrait;
}

The php interpreter will return a fatal error:

Fatal error: Trait method say has not been applied, because there are collisions with other trait methods on TalkingParrot

To resolve this conflict, we could do this:

• use keyword insteadof to use the method from one trait instead of method from another trait
• create an alias for the method with a construct like WoofTrait::say as sayAsDog;

class TalkingParrotV2 extends UnMuteAnimals {
    use MeowTrait, WoofTrait {
        MeowTrait::say insteadof WoofTrait;
        WoofTrait::say as sayAsDog;
    }
}

$talkingParrot = new TalkingParrotV2();
$talkingParrot->say();
$talkingParrot->sayAsDog();

This code will produce the following output:

Meow

Woof