PHP 8.3 Changes

PHP 8.3 added typed class constants, the #[\Override] attribute, dynamic class-constant fetching, readonly cloning amendments, and json_validate(). These changes are useful for safer maintenance and library code.

Changes Worth Recognising

• Typed class constants make inherited configuration contracts clearer.
• #[\Override] catches misspelled or stale overriding methods.
• json_validate() checks JSON syntax without building a decoded value.
• Readonly properties can be reinitialised during cloning from class scope.

Representative Code

<?php

interface Formatter
{
    public function format(string $value): string;
}

final class UpperFormatter implements Formatter
{
    #[\Override]
    public function format(string $value): string
    {
        return strtoupper($value);
    }
}

echo (new UpperFormatter())->format('php') . PHP_EOL;

// Prints:
// PHP

Upgrade Review

• Add #[\Override] where subclasses and implementations deliberately override behaviour.
• Use json_validate() only when syntax validation is enough; decode when the application needs the data.
• Review clone behaviour in readonly value objects.

The override attribute is a low-cost maintenance win because it turns accidental method drift into an immediate error.