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c5dbfb64e5* [Capability] Do not announce an externally loaded registry as changed `Registry` suppresses its `*ListChangedEvent`s while it is loading — `dispatch()` returns early on the `loading` guard, so the elements a loader registers are the registry's initial contents rather than a change to them. `testListChangedEventsAreSuppressedDuringTheDeferredLoad` pins that. The guard only covers `Registry::load()`, which needs the loader the constructor took. A registry the caller built cannot be given one that way, so `Builder::resolve()` loads it from the outside instead — by calling `$chainLoader->load($registry)` directly, which never sets the guard. Every element then dispatches on the way in. With a notification bus configured that is not quiet. `PublishingEventDispatcher` turns each event into a published notification, so every `build()` puts one `list_changed` per element on the bus for a registry that did not change. Under PHP-FPM, where the server is built per request and `Psr16NotificationBus` is shared and persistent, every request broadcasts its whole element list to every open `subscriptions/listen` stream and consumes the 256-entry backlog — after which a reader that fell behind silently skips real notifications. Split the guarded body of `load()` into `loadFrom(LoaderInterface $loader)` and route the custom-registry branch through it. `loadFrom()` takes only the `loading` guard, not the `loaded` bookkeeping, which stays with `load()`. The loader it runs belongs to the caller, so it cannot stand in for the one the registry was constructed with: marking the registry loaded would retire a constructor loader that never ran, and would make a second `loadFrom()` — one registry handed to two builders — a silent no-op. Keeping `loaded` out of it also keeps `load()`'s promise that a transient failure is retried on the next read, including when the failing loader reads the registry during its own run. `RegistryInterface` declares no `load()`, so this stays on the concrete `Registry`, and a third-party implementation keeps the path it has today. * Apply batched suggestions from code review Co-authored-by: Christopher Hertel <mail@christopher-hertel.de> |
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MCP PHP SDK
The official PHP SDK for the Model Context Protocol (MCP). It provides a framework-agnostic API for implementing MCP
servers and clients in PHP — tools, resources, prompts, STDIO and HTTP transports, sessions, authorization, and both
protocol eras (the initialize handshake and the stateless 2026-07-28 revision).
This project represents a collaboration between the PHP Foundation and the Symfony project. It adopts development practices and standards from the Symfony project, including Coding Standards and the Backward Compatibility Promise.
Until the first major release, this SDK is considered experimental, please see the roadmap for planned next steps and features.
Installation
composer require mcp/sdk
Build a server
A server is a plain PHP class plus three lines of wiring:
use Mcp\Capability\Attribute\McpResource;
use Mcp\Capability\Attribute\McpTool;
use Mcp\Server;
use Mcp\Server\Transport\StdioTransport;
class Calculator
{
/**
* Adds two numbers.
*/
#[McpTool]
public function add(int $a, int $b): int
{
return $a + $b;
}
#[McpResource(uri: 'config://calculator/settings')]
public function settings(): array
{
return ['precision' => 2];
}
}
exit(Server::builder()
->setServerInfo('Calculator', '1.0.0')
->setDiscovery(__DIR__, ['.'], excludeDirs: ['vendor'])
->build()
->run(new StdioTransport()));
The walkthrough in First server explains each piece, and Try it with the Inspector shows it running.
Build a client
use Mcp\Client;
use Mcp\Client\Transport\StdioTransport;
$client = Client::builder()
->setClientInfo('My Application', '1.0.0')
->build();
$client->connect(new StdioTransport(command: 'php', args: ['/path/to/server.php']));
$tools = $client->listTools();
$result = $client->callTool('add', ['a' => 5, 'b' => 3]);
$client->disconnect();
See Connecting to a server for transports, timeouts, and the handlers that answer server-initiated requests.
Documentation
The full documentation is published at php.sdk.modelcontextprotocol.io.
- Get started — Install the SDK and build your first server
- Servers — Tools, resources, resource templates, prompts, and how to register them
- Inside your handler — Talking back to the client, logging, and asking for input
- Running your server — Server builder, STDIO and HTTP transports, framework integration, sessions, authorization
- Clients — Client SDK for connecting to and communicating with MCP servers
- Protocol versions — The two protocol eras, and what revision
2026-07-28changed - Advanced — Events, protocol extensions (including MCP Apps), and custom message handlers
- Examples — Runnable server and client examples
- API Reference — Generated class reference
External Resources
- Model Context Protocol Documentation — Official MCP documentation
- Model Context Protocol Specification — Protocol specification
- Officially Supported Servers — Reference server implementations
PHP Libraries Using the MCP SDK
- api-platform/mcp — MCP integration for API Platform
- bnomei/kirby-mcp — MCP server for the Kirby CMS
- drupal/mcp_server — MCP server for Drupal exposing configuration and entities as MCP elements
- josbeir/cakephp-synapse — CakePHP plugin exposing application functionality over MCP
- nette/mcp-inspector — MCP server for introspecting Nette applications
- symfony/ai-mate — AI development assistant MCP server for Symfony projects
- symfony/mcp-bundle — Symfony integration bundle
Building something on top of the SDK? Open a pull request to add it to this list.
Contributing
We are passionate about supporting contributors of all levels of experience and would love to see you get involved in the project. Start by reporting issues or sending pull requests. See CONTRIBUTING.md for development setup, coding standards, and what to run before opening a PR.
Credits
The starting point for this SDK was the PHP-MCP project, initiated by Kyrian Obikwelu, and the Symfony AI initiative. We are grateful for the work done by both projects and their contributors, which created a solid foundation for this SDK.
License
This project is licensed under the Apache License, Version 2.0 for new contributions, with existing code under the MIT License — see the LICENSE file for details.