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PHP Traits vs Interfaces: When to Use Each

Claude

Traits and interfaces both help with code reuse, but they solve opposite problems — an interface defines a contract with no implementation, while a trait provides actual implementation you can mix into unrelated classes.

Interfaces: Contracts

interface Loggable {
    public function getLogMessage(): string;
}

class OrderCreated implements Loggable {
    public function getLogMessage(): string {
        return "Order created";
    }
}

Traits: Shared Implementation

trait Timestampable {
    private ?DateTime $createdAt = null;

    public function touch(): void {
        $this->createdAt = new DateTime();
    }
}

class Post {
    use Timestampable;
}

class Comment {
    use Timestampable;  // same behavior, unrelated class hierarchy
}

Use an interface when you need polymorphism (many classes, one contract). Use a trait when you need to share actual code across classes that have no logical inheritance relationship to each other.

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