feat(session): implement PSR-16 cache based session storage (#114)

Author: lvluoyue

README.md

@@ -190,23 +190,42 @@ $response = $server->run($transport);
 By default, the SDK uses in-memory sessions. You can configure different session stores:
 
 ```php
-use Mcp\Server\Session\InMemorySessionStore;
 use Mcp\Server\Session\FileSessionStore;
+use Mcp\Server\Session\InMemorySessionStore;
+use Mcp\Server\Session\Psr16StoreSession;
+use Symfony\Component\Cache\Psr16Cache;
+use Symfony\Component\Cache\Adapter\RedisAdapter;
 
-// Use default in-memory sessions (TTL only)
+// Use default in-memory sessions with custom TTL
 $server = Server::builder()
     ->setSession(ttl: 7200) // 2 hours
     ->build();
 
-// Use file-based sessions
+// Override with file-based storage
 $server = Server::builder()
     ->setSession(new FileSessionStore(__DIR__ . '/sessions'))
     ->build();
 
-// Use in-memory with custom TTL
+// Override with in-memory storage and custom TTL
 $server = Server::builder()
     ->setSession(new InMemorySessionStore(3600))
     ->build();
+
+// Override with PSR-16 cache-based storage
+// Requires psr/simple-cache and symfony/cache (or any other PSR-16 implementation)
+// composer require psr/simple-cache symfony/cache
+$redisAdapter = new RedisAdapter(
+    RedisAdapter::createConnection('redis://localhost:6379'),
+    'mcp_sessions'
+);
+
+$server = Server::builder()
+    ->setSession(new Psr16StoreSession(
+        cache: new Psr16Cache($redisAdapter),
+        prefix: 'mcp-',
+        ttl: 3600
+    ))
+    ->build();
 ```
 
 ### Discovery Caching

docs/server-builder.md

@@ -139,6 +139,9 @@ Configure session storage and lifecycle. By default, the SDK uses `InMemorySessi
 ```php
 use Mcp\Server\Session\FileSessionStore;
 use Mcp\Server\Session\InMemorySessionStore;
+use Mcp\Server\Session\Psr16StoreSession;
+use Symfony\Component\Cache\Psr16Cache;
+use Symfony\Component\Cache\Adapter\RedisAdapter;
 
 // Use default in-memory sessions with custom TTL
 $server = Server::builder()
@@ -147,18 +150,35 @@ $server = Server::builder()
 
 // Override with file-based storage
 $server = Server::builder()
-    ->setSession(new FileSessionStore('/tmp/mcp-sessions'))
+    ->setSession(new FileSessionStore(__DIR__ . '/sessions'))
     ->build();
 
 // Override with in-memory storage and custom TTL
 $server = Server::builder()
     ->setSession(new InMemorySessionStore(3600))
     ->build();
+
+// Override with PSR-16 cache-based storage
+// Requires psr/simple-cache and symfony/cache (or any other PSR-16 implementation)
+// composer require psr/simple-cache symfony/cache
+$redisAdapter = new RedisAdapter(
+    RedisAdapter::createConnection('redis://localhost:6379'),
+    'mcp_sessions'
+);
+
+$server = Server::builder()
+    ->setSession(new Psr16StoreSession(
+        cache: new Psr16Cache($redisAdapter),
+        prefix: 'mcp-',
+        ttl: 3600
+    ))
+    ->build();
 ```
 
 **Available Session Stores:**
 - `InMemorySessionStore`: Fast in-memory storage (default)
 - `FileSessionStore`: Persistent file-based storage
+- `Psr16StoreSession`: PSR-16 compliant cache-based storage
 
 **Custom Session Stores:**
 

src/Server/Session/Psr16StoreSession.php

@@ -0,0 +1,81 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * 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\Server\Session;
+
+use Psr\SimpleCache\CacheInterface;
+use Symfony\Component\Uid\Uuid;
+
+/**
+ * @author luoyue <1569097443@qq.com>
+ *
+ * PSR-16 compliant cache-based session store.
+ *
+ * This implementation uses any PSR-16 compliant cache as the storage backend
+ * for session data. Each session is stored with a prefixed key using the session ID.
+ */
+class Psr16StoreSession implements SessionStoreInterface
+{
+    public function __construct(
+        private readonly CacheInterface $cache,
+        private readonly string $prefix = 'mcp-',
+        private readonly int $ttl = 3600,
+    ) {
+    }
+
+    public function exists(Uuid $id): bool
+    {
+        try {
+            return $this->cache->has($this->getKey($id));
+        } catch (\Throwable) {
+            return false;
+        }
+    }
+
+    public function read(Uuid $id): string|false
+    {
+        try {
+            return $this->cache->get($this->getKey($id), false);
+        } catch (\Throwable) {
+            return false;
+        }
+    }
+
+    public function write(Uuid $id, string $data): bool
+    {
+        try {
+            return $this->cache->set($this->getKey($id), $data, $this->ttl);
+        } catch (\Throwable) {
+            return false;
+        }
+    }
+
+    public function destroy(Uuid $id): bool
+    {
+        try {
+            return $this->cache->delete($this->getKey($id));
+        } catch (\Throwable) {
+            return false;
+        }
+    }
+
+    public function gc(): array
+    {
+        return [];
+    }
+
+    private function getKey(Uuid $id): string
+    {
+        return $this->prefix.$id;
+    }
+}