PHP 8.3 and Interface Properties

[hskrasek]

Alright I've thrown together a half-ass recreation in the Playground but it's hard to do the full thing without basically copy-pasting a ton of Laravel classes. But I for the life of me cannot figure out why PHPStan doesn't see these properties.

https://phpstan.org/r/58cdf392-e5a0-4915-aaff-cec675b5e27c

I tried following this section of the docs but it doesn't seem to match or work with how we are doing things. I can't tell if this is a "you're doing it wrong" issue or a "phpstan is being weird" issue https://phpstan.org/blog/solving-phpstan-access-to-undefined-property#making-%40property-phpdoc-above-interfaces-work-on-php-8.2%2B

What we're trying to accomplish is a shared interface that objects implement the interface with defined properties as they are shared across all implementing objects. I'm starting to think this is an issue of "just use an abstract class" but we don't really need an abstract class in this implementation.

Am I just approaching this completely wrong as I try to make more type safe PHP code?

[ondrejmirtes]

What class in the end implements AttributeCosts interface?

[hskrasek]

I have a few examples:

<?php

declare(strict_types=1);

namespace App\Costs\Hvac;

use App\Costs\AttributeCosts;
use App\Costs\Concerns\HasExtra;

final readonly class AttributeCost implements AttributeCosts, HasExtra
{
    /**
     * @param array{details: array<string, string|float|null>} $attributes
     */
    public function __construct(
        public string $systemType,
        public string $unitType,
        public ?string $homeSize,
        public ?string $fuelType,
        public array $attributes,
        public float $materialLow,
        public float $materialHigh,
        public float $laborLow,
        public float $laborHigh,
        public float $demoLow,
        public float $demoHigh,
        public float $projectMgtLow,
        public float $projectMgtHigh,
        public float $totalLow,
        public float $totalHigh,
    ) {
    }

    /**
     * @return array{details: array<string, string|float|null>}
     */
    #[\Override]
    public function getExtra(): array
    {
        return $this->attributes;
    }
}

<?php

declare(strict_types=1);

namespace App\Costs\Siding;

use App\Costs\AttributeCosts;

/**
 * @property-read string $name
 * @property-read string $material
 * @property-read float $materialLow
 * @property-read float $materialHigh
 * @property-read float $laborLow
 * @property-read float $laborHigh
 * @property-read float $demoLow
 * @property-read float $demoHigh
 * @property-read float $projectMgtLow
 * @property-read float $projectMgtHigh
 * @property-read float $totalLow
 * @property-read float $totalHigh
 */
final readonly class AttributeCost implements AttributeCosts
{
    public function __construct(
        public string $material,
        public float $materialLow,
        public float $materialHigh,
        public float $laborLow,
        public float $laborHigh,
        public float $demoLow,
        public float $demoHigh,
        public float $projectMgtLow,
        public float $projectMgtHigh,
        public float $totalLow,
        public float $totalHigh,
        public ?string $name = null,
    ) {
    }
}

[hskrasek]

Oddly enough the transformer class also complains about the getExtra method not existing, even though the generic is hinted as an intersection of the interfaces AttributeCosts and HasExtra which is confusing me as well.

[ondrejmirtes]

You should typehint Hvac\AttributeCost|Siding\AttributeCost instead of the AttributeCosts interface. That would make the problem go away.

If there's a lot of classes like that, you can create a type alias: https://phpstan.org/writing-php-code/phpdoc-types#local-type-aliases

The problem is that you can't declare properties on interfaces. So @property above an interface does not enforce anything. It's a hack and you're better off getting rid of it :)

[mad-briller]

@property annotations above a contract make no guarantees about the properties being available on implementers. As such phpstan ignores them unless it can tell for certain that magic properties are supported.

You have two options:

1. As Ondrej is probably going to suggest, you can use @require-extends on your interface, if for example it's expected that the AttributeCosts implementor always extends an Eloquent model:
   https://phpstan.org/writing-php-code/phpdocs-basics#enforcing-class-inheritance-for-interfaces-and-traits

2. Enforce that classes implementing the interface expose magic properties by defining __get as part of the interface:
   https://phpstan.org/r/c5863959-a52d-43e3-9f21-52fc149ff94e

[hskrasek]

@mad-briller Yea I was having a hard time getting the @require-extends to work because it doesn't match our use-case. I'm guessing the expectation is that we'd have some sort of abstract or concrete class that all the implementing classes extend, which either has the properties, or the __get method?

[mad-briller]

I'm guessing the expectation is that we'd have some sort of abstract or concrete class that all the implementing classes extend, which either has the properties, or the __get method?

yeah this is correct i believe, though i haven't used @require-extends yet myself so might be worth having a play yourself.