model example for typed properties

typed-property.php

<?php

declare(strict_types=1);

final class Foo
{
    var DateTimeImmutable $createdAt {
        get;
        private set(DateTimeImmutable $value) : void {
            assert($this->createdAt === null, "Can't change time of creation.");
            
            $this->createdAt = $value;
        };
    }

    var DateTimeImmutable $updatedAt {
        get;
        set(DateTimeImmutable $value) : void {
            assert($value > $this->createdAt, "Can't be updated earlier than created, are you coming from future?");
            assert($value->format('w') !== '6', "Don't work on Sundays. :)");

            $this->updatedAt = $value;
        };
    }
    
    public function __construct()
    {
        $this->createdAt = new DateTimeImmutable();
    }
}

$foo = new Foo();
$foo->updatedAt = new DateTimeImmutable();