PHP 8.5 `clone()` With Changed Properties

PHP 8.5 turns cloning into a function form that can reassign selected properties while copying an object. This is especially useful for readonly value objects that need a clear “with changed value” operation.

Changes Worth Recognising

• Use clone($object, ["property" => $value]) to create a modified copy.
• The original object is not mutated.
• Keep property names reviewable and cover copy operations with tests.
• Value-object copying does not make referenced objects deeply immutable.

Copy a Readonly Value

<?php

readonly class Page
{
    public function __construct(
        public string $title,
        public bool $published,
    ) {}

    public function publish(): self
    {
        return clone($this, ['published' => true]);
    }
}

$draft = new Page('PHP 8.5', false);
$published = $draft->publish();

echo $draft->published ? "live\n" : "draft\n";
echo $published->published ? "live\n" : "draft\n";

// Prints:
// draft
// live

Upgrade Review

• Perform readonly property changes from a scope allowed to write those properties.
• Test that the original remains unchanged.
• Review nested object references when deep independence matters.
• Use a named method when the domain transition needs validation or side effects.

Use this syntax inside a value-object method for simple copy-with changes; retain domain methods for transitions with business rules.