feat(server): Rework transport architecture and add StreamableHttpTransport (#49)

* feat(server): Rework transport architecture and add StreamableHttpTransport

- `Server::connect()` no longer contains a processing loop.
- `TransportInterface` is updated with `setMessageHandler()` and `listen()`.
- `StdioTransport` is updated to implement the new interface.
- A new, minimal `StreamableHttpTransport` is added for stateless HTTP.

* refactor(server): use  event-driven message handling

* feat(server): Introduce a formal session management system

* fix: ensure session elements are preserved when building server (regression from #46)

* refactor: consolidate HTTP example to use shared dependencies

* feat(server): Enhance message handling with session support

- Updated `TransportInterface` to use `onMessage` for handling incoming messages with session IDs.
- Refactored `Server`, `Handler`, and transport classes to accommodate session management using `Uuid`.
- Introduced methods for creating sessions with auto-generated and specific UUIDs in `SessionFactory` and `SessionFactoryInterface`.

* feat(server): Integrate session management in message handling

- Added session support to the `Server` and `Handler` classes, allowing for session data to be managed during message processing.
- Updated `TransportInterface` to include session context in the `send` method.
- Refactored various request handlers to utilize session information, ensuring proper session handling for incoming requests.
- Introduced a file-based session store for persistent session data management

* feat: Update session builder method to use set* instead of with*

* feat: Fix test compatibility with new session management architecture

* chore: apply code style fixes

* fix: remove deprecated SSE transport and resolve PHPStan issues

examples/10-simple-http-transport/McpElements.php

@@ -0,0 +1,118 @@
+<?php
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Mcp\Example\HttpTransportExample;
+
+use Mcp\Capability\Attribute\McpPrompt;
+use Mcp\Capability\Attribute\McpResource;
+use Mcp\Capability\Attribute\McpTool;
+
+class McpElements
+{
+    public function __construct()
+    {
+    }
+
+    /**
+     * Get the current server time.
+     */
+    #[McpTool(name: 'current_time')]
+    public function getCurrentTime(string $format = 'Y-m-d H:i:s'): string
+    {
+        try {
+            return date($format);
+        } catch (\Exception $e) {
+            return date('Y-m-d H:i:s'); // fallback
+        }
+    }
+
+    /**
+     * Calculate simple math operations.
+     */
+    #[McpTool(name: 'calculate')]
+    public function calculate(float $a, float $b, string $operation): float|string
+    {
+        return match (strtolower($operation)) {
+            'add', '+' => $a + $b,
+            'subtract', '-' => $a - $b,
+            'multiply', '*' => $a * $b,
+            'divide', '/' => 0 != $b ? $a / $b : 'Error: Division by zero',
+            default => 'Error: Unknown operation. Use: add, subtract, multiply, divide',
+        };
+    }
+
+    /**
+     * Server information resource.
+     *
+     * @return array{status: string, timestamp: int, version: string, transport: string, uptime: int}
+     */
+    #[McpResource(
+        uri: 'info://server/status',
+        name: 'server_status',
+        description: 'Current server status and information',
+        mimeType: 'application/json'
+    )]
+    public function getServerStatus(): array
+    {
+        return [
+            'status' => 'running',
+            'timestamp' => time(),
+            'version' => '1.0.0',
+            'transport' => 'HTTP',
+            'uptime' => time() - $_SERVER['REQUEST_TIME'],
+        ];
+    }
+
+    /**
+     * Configuration resource.
+     *
+     * @return array{debug: bool, environment: string, timezone: string, locale: string}
+     */
+    #[McpResource(
+        uri: 'config://app/settings',
+        name: 'app_config',
+        description: 'Application configuration settings',
+        mimeType: 'application/json'
+    )]
+    public function getAppConfig(): array
+    {
+        return [
+            'debug' => $_SERVER['DEBUG'] ?? false,
+            'environment' => $_SERVER['APP_ENV'] ?? 'production',
+            'timezone' => date_default_timezone_get(),
+            'locale' => 'en_US',
+        ];
+    }
+
+    /**
+     * Greeting prompt.
+     *
+     * @return array{role: string, content: string}
+     */
+    #[McpPrompt(
+        name: 'greet',
+        description: 'Generate a personalized greeting message'
+    )]
+    public function greetPrompt(string $firstName = 'World', string $timeOfDay = 'day'): array
+    {
+        $greeting = match (strtolower($timeOfDay)) {
+            'morning' => 'Good morning',
+            'afternoon' => 'Good afternoon',
+            'evening', 'night' => 'Good evening',
+            default => 'Hello',
+        };
+
+        return [
+            'role' => 'user',
+            'content' => "# {$greeting}, {$firstName}!\n\nWelcome to our MCP HTTP Server example. This demonstrates how to use the Model Context Protocol over HTTP transport.",
+        ];
+    }
+}

examples/10-simple-http-transport/README.md

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+# HTTP MCP Server Example
+
+This example demonstrates how to use the MCP SDK with HTTP transport using the StreamableHttpTransport. It provides a complete HTTP-based MCP server that can handle JSON-RPC requests over HTTP POST.
+
+## Usage
+
+**Step 1: Start the HTTP server**
+
+```bash
+cd examples/10-simple-http-transport
+php -S localhost:8000 server.php
+```
+
+**Step 2: Connect with MCP Inspector**
+
+```bash
+npx @modelcontextprotocol/inspector http://localhost:8000
+```
+
+## Available Features
+
+- **Tools**: `current_time`, `calculate`
+- **Resources**: `info://server/status`, `config://app/settings`
+- **Prompts**: `greet`

examples/10-simple-http-transport/server.php

@@ -0,0 +1,40 @@
+<?php
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+require_once dirname(__DIR__).'/bootstrap.php';
+chdir(__DIR__);
+
+use Laminas\HttpHandlerRunner\Emitter\SapiEmitter;
+use Mcp\Server;
+use Mcp\Server\Session\FileSessionStore;
+use Mcp\Server\Transport\StreamableHttpTransport;
+use Nyholm\Psr7\Factory\Psr17Factory;
+use Nyholm\Psr7Server\ServerRequestCreator;
+
+$psr17Factory = new Psr17Factory();
+$creator = new ServerRequestCreator($psr17Factory, $psr17Factory, $psr17Factory, $psr17Factory);
+
+$request = $creator->fromGlobals();
+
+$server = Server::make()
+    ->setServerInfo('HTTP MCP Server', '1.0.0', 'MCP Server over HTTP transport')
+    ->setContainer(container())
+    ->setSession(new FileSessionStore(__DIR__.'/sessions'))
+    ->setDiscovery(__DIR__, ['.'])
+    ->build();
+
+$transport = new StreamableHttpTransport($request, $psr17Factory, $psr17Factory);
+
+$server->connect($transport);
+
+$response = $transport->listen();
+
+(new SapiEmitter())->emit($response);