Embracing PHP 8.4’s Asymmetric Visibility: A Game Changer for Clean Code

PHP continues to evolve with exciting new features, and PHP 8.4’s asymmetric visibility might be one of the most impactful additions for writing cleaner, more maintainable code. This feature fundamentally changes how we control access to class properties, offering elegant solutions to common design challenges.

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What Problem Does Asymmetric Visibility Solve?

For years, PHP developers have followed this pattern:

class User {
    private string $id;
    
    public function getId(): string {
        return $this->id;
    }
    
    // No public setter - ID shouldn't change
}

We wanted public read access but restricted write access. Asymmetric visibility eliminates this boilerplate:

class User {
    public private(set) string $id;
}

Real-World Use Cases

1. E-Commerce: Immutable Order IDs

class Order {
    public function __construct(
        public private(set) string $orderId,
        public private(set) DateTimeImmutable $createdAt,
        private(set) float $total // Shorthand for public private(set)
    ) {
        $this->createdAt = new DateTimeImmutable();
    }
}

// Usage
$order = new Order('ord_123', 99.99);
echo $order->orderId; // Allowed
$order->orderId = 'new_id'; // Fatal error

Why it matters: Prevents accidental modification of critical order data while maintaining easy access.

2. API Clients: Configuration Safety

class ApiClient {
    public function __construct(
        public private(set) string $apiKey,
        public protected(set) string $baseUrl = 'https://api.example.com'
    ) {}
}

class SandboxApiClient extends ApiClient {
    public function useSandbox() {
        $this->baseUrl = 'https://sandbox.api.example.com'; // Allowed in child
    }
}

// Usage
$client = new ApiClient('secret_key');
echo $client->baseUrl; // Allowed
$client->baseUrl = 'malicious.url'; // Fatal error