Modern PHP 8.4 Notes: Strict Types, Readonly DTOs, and Plain Domain Logic
Why core PHP fundamentals matter: exploring strict typing, readonly data transfer objects, and plain domain logic for backend systems.
Modern PHP (8.2 through 8.4) provides a strongly typed, expressive environment for developing dependable backend services and domain logic.
1. The Value of Deep Language Foundations
Frameworks evolve, but understanding language internals—how memory is handled, how opcache operates, and how objects are referenced—helps when debugging production issues.
In my `php-works` repository, I deliberately stepped back from framework abstractions to write raw PHP algorithms, custom data structures, and foundational design patterns.
2. Leveraging Strict Types and Readonly Classes
One of the biggest shifts in modern PHP is strict typing. By enforcing `declare(strict_types=1);` and leveraging `readonly` classes for Data Transfer Objects (DTOs), you eliminate entire categories of runtime bugs before code ever hits production.
Monetary values should never be stored or manipulated as floating-point numbers due to binary floating-point rounding errors; storing amounts as integer cents prevents precision drift in financial calculations.
<?php
declare(strict_types=1);
namespace App\DTO;
final readonly class ClientContractData
{
public function __construct(
public string $clientUuid,
public string $organizationName,
public int $monthlyRetainerCents,
public \DateTimeImmutable $renewalDate,
public array $deliverableKeys = [],
) {}
}Immutable DTOs guarantee that once contract details are hydrated from the database, values cannot be mutated in transit.
3. Domain Logic and Architecture
Good backend development keeps core domain logic separated from HTTP controllers and database queries.
Writing business rules in plain PHP classes with minimal framework coupling keeps tests fast and maintenance straightforward.
Conclusion & Takeaways
Solid foundations outlast syntax trends. Investing in pure PHP craftsmanship ensures that when framework abstractions fail or behave unexpectedly, you have the underlying knowledge to diagnose and fix the issue.