Symfony Components

Symfony Components

Complete reference for all 38 Symfony components — patterns, APIs, configuration, and best practices for PHP 8.3+ and Symfony 7.x.

Component Index

HTTP & Runtime

• HttpFoundation — Object-oriented HTTP requests/responses replacing PHP globals → reference
• HttpKernel — Request handling, kernel events, controller resolution, middleware → reference
• PSR-7 Bridge — Bidirectional HttpFoundation ↔ PSR-7 conversion → reference
• Runtime — Decoupled bootstrapping for multiple runtime environments → reference

Messaging

• Messenger — Sync/async message buses, transports (AMQP, Redis, Doctrine), middleware, envelopes → reference

Console

• Console — CLI commands, input/output handling, helpers, formatters, progress bars → reference

Dependency Injection

• DependencyInjection — Service container, autowiring, compiler passes, tagged services → reference
• Contracts — Decoupled abstractions for interoperability (Cache, EventDispatcher, HttpClient, etc.) → reference

Forms & Validation

• Form — Form creation, field types, events, data transformers, collections, theming → reference
• Validator — JSR-303 constraints, custom validators, groups, severity levels → reference
• OptionsResolver — Option configuration with defaults, validation, normalization, nesting → reference

Cache, Lock & Semaphore

• Cache — PSR-6/PSR-16 adapters, tag-based invalidation, stampede prevention → reference
• Lock — Exclusive resource locking across processes/servers (Redis, PostgreSQL, file) → reference
• Semaphore — Concurrent access with configurable limits (Redis, DynamoDB) → reference

Events & Workflow

• EventDispatcher — Observer/Mediator patterns, listeners, subscribers, priorities → reference
• Workflow — State machines, workflow transitions, guards, metadata, events → reference

Configuration & Expressions

• Config — Configuration loading, validation, caching, tree building, bundle config → reference
• ExpressionLanguage — Safe expression sandbox for business rules, validation, security → reference
• Yaml — YAML parsing, dumping, linting with full data type support → reference

Filesystem, Finder & Process

• Filesystem — Platform-independent file/directory operations, atomic writes, path utils → reference
• Finder — File search with fluent criteria (name, size, date, depth, content) → reference
• Process — Secure system command execution, async processes, output streaming → reference

Serialization & Types

• PropertyAccess — Read/write objects and arrays via string paths (foo.bar[baz]) → reference
• PropertyInfo — Property metadata extraction (types, access, descriptions) → reference
• TypeInfo — PHP type extraction, resolution, and validation → reference
• VarDumper — Enhanced variable debugging with HTML/CLI formatters → reference
• VarExporter — Export PHP data to OPcache-optimized code, lazy ghost/proxy objects → reference

Testing

• BrowserKit — Simulated browser for programmatic HTTP, cookies, history → reference
• DomCrawler — HTML/XML traversal, CSS selectors, form automation → reference
• CssSelector — CSS-to-XPath conversion for DOM querying → reference
• PHPUnit Bridge — Deprecation reporting, time/DNS mocking, parallel tests → reference

Data & Text Utilities

• Uid — UUID (v1–v8) and ULID generation, conversion, Doctrine integration → reference
• Clock — Testable time abstraction with MockClock and DatePoint → reference
• Intl — Internationalization data (languages, countries, currencies, timezones) → reference
• JsonPath — RFC 9535 JSONPath queries on JSON structures → reference
• Mime — MIME message creation for emails and content types → reference
• Ldap — LDAP/Active Directory connections, queries, and management → reference
• Asset — URL generation and versioning for web assets → reference

Quick Patterns

Dependency Injection (Autowiring)

# services.yaml — most services are autowired automatically
services:
    _defaults:
        autowire: true
        autoconfigure: true
    App\:
        resource: '../src/'
        exclude: '../src/{DI,Entity,Kernel.php}'

Define a Route + Controller

use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Routing\Attribute\Route;

class ArticleController
{
    #[Route('/articles/{id}', methods: ['GET'])]
    public function show(int $id): Response
    {
        return new Response("Article $id");
    }
}

Dispatch a Message (Async)

use Symfony\Component\Messenger\MessageBusInterface;

class OrderService
{
    public function __construct(private MessageBusInterface $bus) {}

    public function place(Order $order): void
    {
        $this->bus->dispatch(new OrderPlaced($order->getId()));
    }
}

Create and Validate a Form

$form = $this->createForm(ArticleType::class, $article);
$form->handleRequest($request);

if ($form->isSubmitted() && $form->isValid()) {
    $em->persist($form->getData());
    $em->flush();
    return $this->redirectToRoute('article_list');
}

Cache with Tags

use Symfony\Contracts\Cache\ItemInterface;

$value = $cache->get('products_list', function (ItemInterface $item) {
    $item->expiresAfter(3600);
    $item->tag(['products']);
    return $this->repository->findAll();
});

$cache->invalidateTags(['products']);

Console Command

use Symfony\Component\Console\Attribute\AsCommand;
use Symfony\Component\Console\Command\Command;
use Symfony\Component\Console\Input\InputInterface;
use Symfony\Component\Console\Output\OutputInterface;

#[AsCommand(name: 'app:process', description: 'Process items')]
class ProcessCommand extends Command
{
    protected function execute(InputInterface $input, OutputInterface $output): int
    {
        $output->writeln('Processing...');
        return Command::SUCCESS;
    }
}

Event Subscriber

use Symfony\Component\EventDispatcher\EventSubscriberInterface;

class OrderSubscriber implements EventSubscriberInterface
{
    public static function getSubscribedEvents(): array
    {
        return [OrderPlacedEvent::class => 'onOrderPlaced'];
    }

    public function onOrderPlaced(OrderPlacedEvent $event): void
    {
        // Handle event
    }
}

Workflow Transition

if ($workflow->can($article, 'publish')) {
    $workflow->apply($article, 'publish');
}

Lock a Resource

$lock = $factory->createLock('pdf-generation', ttl: 30);
if ($lock->acquire()) {
    try {
        generatePdf();
    } finally {
        $lock->release();
    }
}

Best Practices

• Target PHP 8.3+ and Symfony 7.x with strict typing
• Use attributes over YAML/XML for routes, commands, message handlers, event listeners
• Prefer autowiring — only register services manually when configuration is needed
• Use Cache Contracts ($cache->get()) over raw PSR-6 for stampede prevention
• Apply validation groups to support multiple form contexts
• Use state machines by default; use workflows only when parallel states are needed
• Create custom constraints for business logic that can't be expressed with built-in ones
• Mock time and DNS in tests using PHPUnit Bridge for deterministic results