MCP PHP SDK

The Model Context Protocol (MCP) lets applications provide context to LLMs in a standardized way, separating the concern of providing context from the LLM interaction itself.

This is the official PHP SDK for it, a collaboration between the PHP Foundation and the Symfony project. With it you can:

• Build MCP servers that expose tools, resources, and prompts to any MCP host.
• Build MCP clients that connect to any MCP server.
• Speak both standard transports: STDIO and Streamable HTTP.

Requirements

PHP 8.1+.

Installation

composer require mcp/sdk

See Installation for the optional PSR packages an HTTP server or client needs.

Example

Create a file server.php:

<?php

require __DIR__.'/vendor/autoload.php';

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];
    }
}

Server::builder()
    ->setServerInfo('Calculator', '1.0.0')
    ->setDiscovery(__DIR__, ['.'], excludeDirs: ['vendor'])
    ->build()
    ->run(new StdioTransport());

That's a complete MCP server. It exposes one tool, add, and one resource, config://calculator/settings.

Attribute discovery needs symfony/finder (composer require symfony/finder). Without it the server still starts, but discovers nothing and only logs a warning.

Look at what you did not write: no JSON Schema — int $a, int $b is the schema — no request parsing, no serialization, no protocol handling. You wrote a PHP class with type hints and a docblock; the SDK does the rest.

First server walks through running it, and Try it with the Inspector opens it in a UI you can click around in.

Where to go next

• Get started takes you from composer require to a server a real MCP host can talk to.
• What a server exposes — tools, resources, prompts — is Servers.
• Getting it in front of clients (STDIO, HTTP, your existing Symfony or Laravel app) is Running your server.
• What is available inside the functions you register is Inside your handler.
• Building the other side, an application that uses MCP servers, is Clients.
• The two protocol eras, and what revision 2026-07-28 changed, are Protocol versions.
• What gets deprecated, for how long, and where the SDK stands on spec-tier support are under Project: Deprecation policy and SDK tier target.
• Complete, runnable projects are in Examples.
• Hunting for an exact signature? The API Reference is generated from the source.