How can you ensure the immutability of a class if it contains public properties?

To ensure the immutability of a class with public properties, you need to control access to these properties and prevent their modification after the object is created.

Main approaches:

• Make properties readonly (if the language supports it) so they can only be set during initialization.
• Use private properties with public getters and no setters.
• If properties are public and mutable, you can return copies of objects (for complex types) so external changes do not affect the internal state.

Example in PHP using constructor and getters:

class ImmutableClass {
    public readonly string $name;
    public readonly int $age;

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

If the PHP version does not support readonly, you can make properties private and add only getters:

class ImmutableClass {
    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;
    }
}

Thus, after creating the object, properties cannot be changed.