haphpiness

Clone With — Modify Properties While Cloning

PHP 8.5 turns clone into a function that accepts property overrides. This is the "wither" pattern that readonly classes desperately needed — create a modified copy without boilerplate.

readonly class Color {
    public function __construct(
        public int $red,
        public int $green,
        public int $blue,
        public int $alpha = 255,
    ) {}

    public function withAlpha(int $alpha): self {
        return clone($this, ['alpha' => $alpha]);
    }

    public function darken(float $factor): self {
        return clone($this, [
            'red'   => (int)($this->red * $factor),
            'green' => (int)($this->green * $factor),
            'blue'  => (int)($this->blue * $factor),
        ]);
    }
}

$blue = new Color(79, 91, 147);
$transparent = $blue->withAlpha(128);
$darkBlue = $blue->darken(0.5);

// $blue is unchanged — immutability preserved
echo $blue->alpha;        // 255
echo $transparent->alpha; // 128

// Works with any class, not just readonly
$modified = clone($request, ['method' => 'POST', 'body' => $payload]);

Before PHP 8.5, creating a modified copy of a readonly object required manually passing every property to the constructor — even the ones that didn't change. clone() with overrides solves this elegantly.