PHP Typed Property

class TypeDemonstration {
    // Scalar types
    public int $integer;
    protected float $floatingPoint;
    private bool $boolean;
    public string $string;

    // Compound and Object types
    public array $array;
    public iterable $iterable;
    public object $object;
    public stdClass $classInstance;

    // Nullable types (prefixed with '?')
    public ?string $nullableString;

    // Default values (must match the declared type)
    public int $withDefault = 42;

    // Union types (PHP 8.0+)
    public int|float $number;

    // Intersection types (PHP 8.1+)
    public Iterator&Countable $traversableCollection;
}

class Entity {
    public int $id;
    public ?string $name;
}

$entity = new Entity();

// Fatal error: Typed property Entity::$id must not be accessed before initialization
echo $entity->id; 

class Counter {
    public int $count = 10;
}

$counter = new Counter();
unset($counter->count);

// Fatal error: Typed property Counter::$count must not be accessed before initialization
echo $counter->count;

declare(strict_types=1);

class StrictExample {
    public int $count;
}

$obj = new StrictExample();
$obj->count = "10"; // TypeError: Cannot assign string to property StrictExample::$count of type int

class ParentClass {
    public $untypedValue;
    public int|float $typedValue;
}

class ChildClass extends ParentClass {
    // Fatal error: Type of ChildClass::$untypedValue must not be defined (as in class ParentClass)
    public int $untypedValue; 

    // Fatal error: Type of ChildClass::$typedValue must be int|float (as in class ParentClass)
    public int $typedValue; 
}