Using property hooks in PHP

Property hooks have existed in PHP since 8.4 - 1.5 years ago now - and whilst they're not something I've reached for often, they do have their place.

Consider the following object.

final readonly class EntityReference
{
    public function __construct(
        public Type $type,
        public string $reference
    ) {}

    public function key(): string
    {
        return "{$this->type->value}:{$this->reference}";
    }
}

// And reference the key as expected
$entity = new EntityReference(Type::Business, 'business-1');
$entity->key(); // businesses:business-1

Fairly commonplace pattern in PHP land. We want to have some kind of derived value on a class, surfaced into the public API by way of a getter.

With property hooks, we can do away with the method entirely by defining a virtual property.

final class EntityReference
{
    public string $key {
        get => "{$this->type->value}:{$this->reference}";
    }

    public function __construct(
        public readonly Type $type,
        public readonly string $reference
    ) {}
}

// Reference the key now as a property
$entity = new EntityReference(Type::Person, 'person-1');
$entity->key; // people:person-1

The subtle difference here is that a class with virtual property hooks is not allowed to be readonly.

By adding the virtual property here, we expose the same data, expose it via a public interface, and keep a consistent property-based access.

I don't reach for these often, but when I have an otherwise property-only data structure, I think it makes more sense to surface computed values as virtual properties rather than methods. I tend to reserve methods for behaviours or complex logic, and defer to virtual properties for simple derived values.