Readonly Classes in PHP 8.2

PHP 8.2 introduces a new concept of readonly classes, which allow developers to prevent objects of a particular class from being modified after they are created. This can be useful for ensuring the integrity of data and reducing the chances of bugs and other issues in a PHP application.

To create a readonly class, developers simply need to use the readonly keyword when defining the class. For example:

readonly class User
{
    private string $name;
    private int $age;

    public function __construct(string $name, int $age)
    {
        $this->name = $name;
        $this->age = $age;
    }

    public function getName(): string
    {
        return $this->name;
    }

    public function getAge(): int
    {
        return $this->age;
    }
}

In this example, the User class is marked as readonly, which means that once an object of this class is created, it cannot be modified. This means that any attempts to change the object’s properties or call methods that modify its state will result in an error.

One important thing to note about readonly classes is that they only prevent modifications to objects of the class, not the class itself. This means that developers can still add, remove, or modify methods and properties of the class, as well as extend it or implement interfaces.

Another key feature of readonly classes is that they are compatible with inheritance. This means that a child class can inherit from a readonly parent class, but it cannot modify the state of objects of the parent class. For example:

readonly class User
{
    private string $name;
    private int $age;

    public function __construct(string $name, int $age)
    {
        $this->name = $name;
        $this->age = $age;
    }

    public function getName(): string
    {
        return $this->name;
    }

    public function getAge(): int
    {
        return $this->age;
    }
}

class Admin extends User
{
    private bool $isAdmin;

    public function __construct(string $name, int $age, bool $isAdmin)
    {
        parent::__construct($name, $age);
        $this->isAdmin = $isAdmin;
    }

    public function getIsAdmin(): bool
    {
        return $this->isAdmin;
    }
}

In this example, the Admin class extends the User class, which is marked as readonly. This means that objects of the Admin class can have their isAdmin property modified, but they cannot be modified in any other way.

Overall, readonly classes in PHP 8.2 provide a useful way for developers to ensure the integrity of their data and prevent unintended modifications to objects. By using this feature, developers can write more robust and reliable PHP applications.

I hope you find this useful. Please comment if you have any questions.

Posted in PHP