PHP — Traits

Basic trait

<?php
trait Timestampable {
    private string $createdAt;
    private string $updatedAt;

    public function setCreatedAt(): void {
        $this->createdAt = date('Y-m-d H:i:s');
    }

    public function getCreatedAt(): string {
        return $this->createdAt ?? '';
    }
}

class Post {
    use Timestampable;

    public function __construct(public string $title) {
        $this->setCreatedAt();
    }
}

$post = new Post("Hello");
echo $post->getCreatedAt();
?>

Multiple traits

<?php
trait Loggable {
    public function log(string $message): void {
        echo "[LOG] $message\n";
    }
}

trait Cacheable {
    private array $cache = [];

    public function cache(string $key, mixed $value): void {
        $this->cache[$key] = $value;
    }

    public function getCache(string $key): mixed {
        return $this->cache[$key] ?? null;
    }
}

class User {
    use Loggable, Cacheable;
}

$user = new User();
$user->log("User created");
$user->cache("name", "Alice");
echo $user->getCache("name");
?>

Trait conflict resolution

<?php
trait A {
    public function show(): void { echo "A\n"; }
}

trait B {
    public function show(): void { echo "B\n"; }
}

class MyClass {
    use A, B {
        B::show insteadof A;
        A::show as showA;
    }
}

$obj = new MyClass();
$obj->show();   // B
$obj->showA();  // A
?>

Abstract methods in traits

<?php
trait Validator {
    abstract public function validate(): bool;

    public function isValid(): bool {
        return $this->validate();
    }
}

class User {
    use Validator;

    public function __construct(private string $name) {}

    public function validate(): bool {
        return !empty($this->name);
    }
}

$user = new User("Alice");
echo $user->isValid() ? "Valid" : "Invalid";
?>

Mini Practice

Write PHP code that:

1. Creates a trait with methods
2. Uses multiple traits in one class
3. Resolves trait conflicts
4. Uses abstract methods in a trait

Up Next

In the next lesson, you'll learn about Error Handling — exceptions in PHP.