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PSRs

Summary

Dotkernel API is built on the PHP-FIG standards, which keep your code portable and let PSR-compliant libraries drop in without adapters. PSR-7 (HTTP messages), PSR-15 (handlers and middleware) and PSR-11 (container) are architectural foundations; PSR-3, PSR-4, PSR-6, PSR-13, PSR-14, PSR-17, PSR-18 and PSR-20 arrive through dependencies.

Why PSRs Matter for Dotkernel API

  • Vendor Lock-In Prevention: By following PSRs, you're not locked into Dotkernel API. Your code can be reused in other PSR-compliant frameworks.
  • Ecosystem Compatibility: Any library that follows PSRs can integrate with Dotkernel API without custom adapters.
  • Team Collaboration: Developers familiar with PSRs can immediately understand Dotkernel API's code structure.
  • Long-Term Maintenance: PSRs are stable standards maintained by the PHP community, ensuring longevity.
  • Code Quality: Following standards encourages best practices and makes code more maintainable.

PHP Standards Recommendations (PSRs)

Dotkernel API adheres to PHP Standards Recommendations (PSRs) established by the PHP-FIG (Framework Interoperability Group). These standards ensure code interoperability and allow Dotkernel API to work seamlessly with other PSR-compliant libraries.

Some PSRs are at the core of Dotkernel API's architecture, while others are installed as dependencies through third-party packages.

Core PSRs (Essential to Dotkernel API)

PSR-7: HTTP Message Interfaces

Repository: php-fig/http-message

Defines standardized interfaces for HTTP messages (requests and responses) and URIs.

Why it matters:

  • Dotkernel API uses PSR-7 for all HTTP communication.
  • Ensures requests and responses follow a universal standard.
  • Allows middleware and handlers to work with consistent interfaces.
  • Implemented via Laminas\Diactoros.

PSR-15: HTTP Server Request Handlers and Middleware

Repository: php-fig/http-server-handler and php-fig/http-server-middleware

Defines the interface for HTTP request handlers and middleware components that process PSR-7 HTTP messages.

Why it matters:

  • Dotkernel API's entire architecture is built on PSR-15.
  • All handlers implement RequestHandlerInterface.
  • Middleware pipeline processes requests in a chain.
  • Single-action handlers follow this pattern for clean separation of concerns.

PSR-11: Container Interface

Repository: php-fig/container

Defines the standard interface for dependency injection containers.

Why it matters:

  • Dotkernel API uses PSR-11 for managing service dependencies.
  • All services are registered in and retrieved from a container.
  • Enables loose coupling between components.
  • Implemented via Laminas\ServiceManager.

Supporting PSRs (Installed via Dependencies)

PSR-3: Logger Interface

Repository: php-fig/log

Provides a standard interface for logging libraries.

Usage: Error handling, debugging, audit trails Implemented in: dotkernel/dot-errorhandler

PSR-4: Autoloader

Repository: php-fig/log

Defines how PHP files are automatically loaded based on namespaces and file paths.

Usage: Automatic class loading without manual require statements Implemented in: Laminas\Loader

PSR-6: Caching Interface

Repository: php-fig/cache

Defines standard interfaces for caching systems to improve application performance.

Usage: Caching query results, configuration, templates Implemented in: dotkernel/dot-cache

Repository: php-fig/link

Describes how to represent hypermedia links independently of serialization format.

Usage: HAL (Hypertext Application Language) resource links Implemented in: mezzio/mezzio-hal

PSR-14: Event Dispatcher

Repository: php-fig/event-dispatcher

Mechanism for event-based extension and collaboration between components.

Usage: Triggering events on user actions, logging events, notifications Implemented in: Third-party packages as needed

PSR-17: HTTP Factories

Repository: php-fig/http-factory

Standard for factories that create PSR-7 compliant HTTP objects.

Usage: Creating requests, responses, and streams programmatically Implemented in: Laminas\Diactoros

PSR-18: HTTP Client

Repository: php-fig/http-client

Interface for sending HTTP requests and receiving HTTP responses.

Usage: Calling external APIs from your Dotkernel API Implemented in: symfony/http-client or similar packages

PSR-20: Clock

Repository: php-fig/clock

Provides a standard interface for reading the system clock.

Usage: Getting current time in a testable way Implemented in: Third-party packages as needed

PSR Implementation Hierarchy

┌───────────────────────────────────────────┐
│  PSR-7: HTTP Messages (Requests/Responses)│
└───────────────────────────────────────────┘
                    ▲
                    │
┌───────────────────────────────────────────┐
│ PSR-15: Handlers & Middleware             │
│ (Process PSR-7 messages)                  │
└───────────────────────────────────────────┘
                    ▲
                    │
┌───────────────────────────────────────────┐
│ PSR-11: Container                         │
│ (Manages services for handlers)           │
└───────────────────────────────────────────┘
                    ▲
                    │
┌───────────────────────────────────────────┐
│ PSR-4: Autoloader                         │
│ (Loads services automatically)            │
└───────────────────────────────────────────┘

FAQ

Q: Which PSRs are essential to the architecture?

A: PSR-7, PSR-15 and PSR-11. Everything else is supporting, arriving through dependencies rather than shaping the design.

Q: What does building on PSRs buy me in practice?

A: Portability. Because your handlers and services depend on standard interfaces rather than framework classes, they can be reused in any other PSR-compliant framework, and third-party PSR libraries integrate without custom adapters.

Q: What implements PSR-7 here?

A: Laminas\Diactoros, which also provides the PSR-17 HTTP factories.

Q: How does PSR-15 show up in the code I write?

A: Every handler implements RequestHandlerInterface and serves a single action, and requests travel through a middleware pipeline. See The new handler structure.

Q: Which container is used?

A: Laminas\ServiceManager, behind the PSR-11 interface. See Dependency injection.

Q: Which PSR governs the file layout?

A: PSR-4 autoloading, which maps namespaces to paths. See File structure.

Q: Do I need to install anything to use PSR-3 logging or PSR-6 caching?

A: No. They come with dotkernel/dot-errorhandler and dotkernel/dot-cache respectively. See Packages.

Q: How do I call an external API from Dotkernel API?

A: Through a PSR-18 HTTP client such as symfony/http-client, so your calling code depends on the interface rather than a specific client.

Q: Are PSR-14 events and PSR-20 clock available out of the box?

A: Not by default. Both are supplied by third-party packages when a project needs them.