Hello PHP Internals,
I'd like to introduce my RFC for discussion: https://wiki.php.net/rfc/short-and-inner-classes
This RFC defines a short class syntax as well as the ability to nest classes inside another class.
This introduces an unprecedented amount of control, flexibility, and expressiveness over how objects
are used and instantiated in PHP. There is a PR (https://github.com/php/php-src/pull/17895) that
implements this functionality -- all test failures are related to different/new/incorrect error
messages being generated. However, the core functionality exists to take for a test ride.
So, what do I mean by "unprecedented amount of control"? With this change, you can declare
an inner class as private or protected, preventing its usage outside of the outer class:
class User {
private class Id {}
public function __construct(public self::Id $id) {}
}
In the above example, the class User is impossible to construct even though it has a
public constructor (except through reflection) because User::Id is private; User::Id cannot be
instantiated, used as a type hint, or even via instanceof outside of the User class
itself. This example isn't practical but demonstrates something that is nearly impossible in
previous versions of PHP, where all classes are essentially publicly accessible from anywhere within
the codebase.
As a number of inner classes will probably be used as DTOs, the RFC introduces a "short
syntax" for declaring classes, which enhances expressiveness, even allowing the usage of
traits, all in a single line:
// declare a readonly Point, that implements Vector2 and uses the Evolvable trait
readonly class Point(public int $x, public int $y) implements Vector2 use Evolvable;
When combined with inner classes, it looks something like this:
class Pixel {
public readonly class Point(public int $x, public int $y) implements Vector2 use Evolvable;
}
// Create a new pixel point with property $x and $y set to 0
$p = new Pixel::Point(0, 0);
There are far more details in the RFC itself, so please check it out. I'm quite excited to hear
your thoughts!
— Rob
PS. I know I tend to rush into things, but I want to make it clear that I'm not rushing this --
I've learned from my mistakes (thank you to those who have given me advice). I'm going to
do this right.