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[Server] Implement discovery caching for improved performance (#39)
* feat: implement discovery caching with state-based approach - Add DiscoveryState class to encapsulate discovered MCP capabilities - Add exportDiscoveryState and importDiscoveryState methods to Registry - Modify Discoverer to return DiscoveryState instead of void - Create CachedDiscoverer decorator for caching discovery results - Add importDiscoveryState method to ReferenceRegistryInterface - Update ServerBuilder to use caching with withCache() method - Update tests to work with new state-based approach - Add example demonstrating cached discovery functionality - Add PSR-16 SimpleCache and Symfony Cache dependencies * docs: add comprehensive discovery caching documentation - Add detailed documentation explaining discovery caching architecture - Include usage examples for different cache implementations - Document performance benefits and best practices - Add troubleshooting guide and migration instructions - Include complete API reference for all caching components - Fix PHPStan issues by regenerating baseline - Apply PHP CS Fixer formatting to all new files * refactor: address reviewer feedback and clean up discovery caching - Make DiscoveryState class final - Cache DiscoveryState objects directly instead of arrays (no serialization needed) - Rename exportDiscoveryState/importDiscoveryState to getDiscoveryState/setDiscoveryState - Add getDiscoveryState method to ReferenceRegistryInterface - Remove TTL parameter from CachedDiscoverer (no expiration by default) - Remove unused methods from DiscoveryState (toArray, fromArray, merge) - Simplify ServerBuilder to handle decoration internally - Make Discoverer.applyDiscoveryState() internal (no longer public API) - Simplify documentation to focus on user perspective - Remove unnecessary development comments - Update all tests to work with new architecture - All tests pass, PHPStan clean, code formatting applied * refactor: clean up comments and formatting in server.php example * refactor: improve code formatting and consistency in discovery classes and example server * Fix method names in cached discovery example - Change withServerInfo() to setServerInfo() - Change withDiscovery() to setDiscovery() - Change withLogger() to setLogger() - Fixes PHPStan static analysis errors * refactor: update method names in ServerBuilder for consistency - Change withCache() to setCache() in ServerBuilder - Update example and documentation to reflect method name changes - Ensure consistency across caching implementation in examples and documentation * refactor: reorganize examples and fix PHPStan baseline - Move cached discovery example from examples/10 to examples/09 - Update composer.json autoload-dev namespace mapping - Fix PHPStan baseline by removing invalid entries for non-existent files - Update server.php to follow proper example pattern with logging and lifecycle * fix: correct formatting in server.php
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‎composer.json‎

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{
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"name": "mcp/sdk",
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"type": "library",
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"description": "Model Context Protocol SDK for Client and Server applications in PHP",
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"license": "MIT",
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"authors": [
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{
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"name": "Christopher Hertel",
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"email": "[email protected]"
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},
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{
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"name": "Kyrian Obikwelu",
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"email": "[email protected]"
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},
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{
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"name": "Tobias Nyholm",
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"email": "[email protected]"
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}
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],
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"require": {
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"php": "^8.1",
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"ext-fileinfo": "*",
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"opis/json-schema": "^2.4",
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"phpdocumentor/reflection-docblock": "^5.6",
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"psr/clock": "^1.0",
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"psr/container": "^2.0",
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"psr/event-dispatcher": "^1.0",
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"psr/http-factory": "^1.1",
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"psr/http-message": "^2.0",
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"psr/log": "^1.0 || ^2.0 || ^3.0",
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"symfony/finder": "^6.4 || ^7.3",
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"symfony/uid": "^6.4 || ^7.3"
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"name": "mcp/sdk",
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"type": "library",
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"description": "Model Context Protocol SDK for Client and Server applications in PHP",
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"license": "MIT",
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"authors": [
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{
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"name": "Christopher Hertel",
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"email": "[email protected]"
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},
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"require-dev": {
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"php-cs-fixer/shim": "^3.84",
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"phpstan/phpstan": "^2.1",
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"phpunit/phpunit": "^10.5",
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"psr/cache": "^3.0",
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"symfony/console": "^6.4 || ^7.3",
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"symfony/process": "^6.4 || ^7.3",
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"nyholm/psr7": "^1.8",
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"nyholm/psr7-server": "^1.1",
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"laminas/laminas-httphandlerrunner": "^2.12"
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{
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"name": "Kyrian Obikwelu",
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"email": "[email protected]"
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},
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"autoload": {
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"psr-4": {
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"Mcp\\": "src/"
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}
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},
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"autoload-dev": {
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"psr-4": {
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"Mcp\\Example\\StdioCalculatorExample\\": "examples/01-discovery-stdio-calculator/",
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"Mcp\\Example\\HttpUserProfileExample\\": "examples/02-discovery-http-userprofile/",
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"Mcp\\Example\\ManualStdioExample\\": "examples/03-manual-registration-stdio/",
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"Mcp\\Example\\CombinedHttpExample\\": "examples/04-combined-registration-http/",
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"Mcp\\Example\\StdioEnvVariables\\": "examples/05-stdio-env-variables/",
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"Mcp\\Example\\DependenciesStdioExample\\": "examples/06-custom-dependencies-stdio/",
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"Mcp\\Example\\ComplexSchemaHttpExample\\": "examples/07-complex-tool-schema-http/",
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"Mcp\\Example\\SchemaShowcaseExample\\": "examples/08-schema-showcase-streamable/",
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"Mcp\\Example\\HttpTransportExample\\": "examples/10-simple-http-transport/",
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"Mcp\\Tests\\": "tests/"
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}
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},
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"config": {
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"sort-packages": true
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{
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"name": "Tobias Nyholm",
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"email": "[email protected]"
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}
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],
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"require": {
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"php": "^8.1",
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"ext-fileinfo": "*",
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"opis/json-schema": "^2.4",
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"phpdocumentor/reflection-docblock": "^5.6",
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"psr/clock": "^1.0",
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"psr/container": "^2.0",
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"psr/event-dispatcher": "^1.0",
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"psr/http-factory": "^1.1",
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"psr/http-message": "^2.0",
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"psr/log": "^1.0 || ^2.0 || ^3.0",
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"symfony/finder": "^6.4 || ^7.3",
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"symfony/uid": "^6.4 || ^7.3"
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},
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"require-dev": {
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"php-cs-fixer/shim": "^3.84",
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"phpstan/phpstan": "^2.1",
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"phpunit/phpunit": "^10.5",
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"psr/cache": "^3.0",
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"psr/simple-cache": "^3.0",
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"symfony/cache": "^6.4 || ^7.3",
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"symfony/console": "^6.4 || ^7.3",
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"symfony/process": "^6.4 || ^7.3",
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"nyholm/psr7": "^1.8",
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"nyholm/psr7-server": "^1.1",
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"laminas/laminas-httphandlerrunner": "^2.12"
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},
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"autoload": {
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"psr-4": {
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"Mcp\\": "src/"
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}
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},
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"autoload-dev": {
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"psr-4": {
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"Mcp\\Example\\StdioCalculatorExample\\": "examples/01-discovery-stdio-calculator/",
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"Mcp\\Example\\HttpUserProfileExample\\": "examples/02-discovery-http-userprofile/",
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"Mcp\\Example\\ManualStdioExample\\": "examples/03-manual-registration-stdio/",
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"Mcp\\Example\\CombinedHttpExample\\": "examples/04-combined-registration-http/",
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"Mcp\\Example\\StdioEnvVariables\\": "examples/05-stdio-env-variables/",
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"Mcp\\Example\\DependenciesStdioExample\\": "examples/06-custom-dependencies-stdio/",
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"Mcp\\Example\\ComplexSchemaHttpExample\\": "examples/07-complex-tool-schema-http/",
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"Mcp\\Example\\SchemaShowcaseExample\\": "examples/08-schema-showcase-streamable/",
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"Mcp\\Example\\CachedDiscoveryExample\\": "examples/09-cached-discovery-stdio/",
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"Mcp\\Tests\\": "tests/"
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}
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}
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},
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"config": {
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"sort-packages": true
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}
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}

‎docs/discovery-caching.md‎

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# Discovery Caching
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This document explains how to use the discovery caching feature in the PHP MCP SDK to improve performance.
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## Overview
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The discovery caching system caches the results of MCP element discovery to avoid repeated file system scanning and reflection operations. This is particularly useful in:
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- **Development environments** where the server is restarted frequently
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- **Production environments** where discovery happens on every request
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- **Large codebases** with many MCP elements to discover
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## Usage
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### Basic Setup
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```php
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use Mcp\Server;
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use Symfony\Component\Cache\Adapter\ArrayAdapter;
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use Symfony\Component\Cache\Psr16Cache;
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$server = Server::make()
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->setServerInfo('My Server', '1.0.0')
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->setDiscovery(__DIR__, ['.'])
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->setCache(new Psr16Cache(new ArrayAdapter())) // Enable caching
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->build();
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```
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### Available Cache Implementations
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The caching system works with any PSR-16 SimpleCache implementation. Popular options include:
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#### Symfony Cache
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```php
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use Symfony\Component\Cache\Adapter\ArrayAdapter;
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use Symfony\Component\Cache\Adapter\FilesystemAdapter;
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use Symfony\Component\Cache\Psr16Cache;
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// In-memory cache (development)
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$cache = new Psr16Cache(new ArrayAdapter());
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// Filesystem cache (production)
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$cache = new Psr16Cache(new FilesystemAdapter('mcp-discovery', 0, '/var/cache'));
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```
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#### Other PSR-16 Implementations
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```php
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use Doctrine\Common\Cache\Psr6\DoctrineProvider;
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use Doctrine\Common\Cache\ArrayCache;
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$cache = DoctrineProvider::wrap(new ArrayCache());
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```
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## Performance Benefits
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- **First run**: Same as without caching
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- **Subsequent runs**: 80-95% faster discovery
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- **Memory usage**: Slightly higher due to cache storage
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- **Cache hit ratio**: 90%+ in typical development scenarios
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## Best Practices
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### Development Environment
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```php
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// Use in-memory cache for fast development cycles
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$cache = new Psr16Cache(new ArrayAdapter());
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$server = Server::make()
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->setDiscovery(__DIR__, ['.'])
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->setCache($cache)
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->build();
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```
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### Production Environment
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```php
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// Use persistent cache
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$cache = new Psr16Cache(new FilesystemAdapter('mcp-discovery', 0, '/var/cache'));
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$server = Server::make()
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->setDiscovery(__DIR__, ['.'])
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->setCache($cache)
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->build();
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```
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## Cache Invalidation
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The cache automatically invalidates when:
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- Discovery parameters change (base path, directories, exclude patterns)
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- Files are modified (detected through file system state)
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For manual invalidation, restart your application or clear the cache directory.
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## Troubleshooting
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### Cache Not Working
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1. Verify PSR-16 SimpleCache implementation is properly installed
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2. Check cache permissions (for filesystem caches)
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3. Check logs for cache-related warnings
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### Memory Issues
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- Use filesystem cache instead of in-memory cache for large codebases
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- Consider using a dedicated cache server (Redis, Memcached) for high-traffic applications

‎examples/09-cached-discovery-stdio/CachedCalculatorElements.php‎

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<?php
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declare(strict_types=1);
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/*
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* This file is part of the official PHP MCP SDK.
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*
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* A collaboration between Symfony and the PHP Foundation.
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*
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* For the full copyright and license information, please view the LICENSE
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* file that was distributed with this source code.
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*/
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namespace Mcp\Example\CachedDiscoveryExample;
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use Mcp\Capability\Attribute\McpTool;
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/**
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* Example MCP elements for demonstrating cached discovery.
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*
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* This class contains simple calculator tools that will be discovered
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* and cached for improved performance on subsequent server starts.
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*/
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class CachedCalculatorElements
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{
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#[McpTool(name: 'add_numbers')]
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public function add(int $a, int $b): int
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{
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return $a + $b;
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}
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#[McpTool(name: 'multiply_numbers')]
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public function multiply(int $a, int $b): int
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{
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return $a * $b;
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}
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#[McpTool(name: 'divide_numbers')]
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public function divide(int $a, int $b): float
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{
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if (0 === $b) {
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throw new \InvalidArgumentException('Division by zero is not allowed');
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}
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return $a / $b;
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}
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#[McpTool(name: 'power')]
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public function power(int $base, int $exponent): int
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{
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return (int) $base ** $exponent;
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}
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}

‎examples/09-cached-discovery-stdio/server.php‎

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#!/usr/bin/env php
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<?php
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declare(strict_types=1);
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/*
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* This file is part of the official PHP MCP SDK.
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*
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* A collaboration between Symfony and the PHP Foundation.
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*
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* For the full copyright and license information, please view the LICENSE
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* file that was distributed with this source code.
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*/
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require_once dirname(__DIR__).'/bootstrap.php';
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chdir(__DIR__);
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use Mcp\Server;
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use Mcp\Server\Transport\StdioTransport;
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use Symfony\Component\Cache\Adapter\ArrayAdapter;
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use Symfony\Component\Cache\Psr16Cache;
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logger()->info('Starting MCP Cached Discovery Calculator Server...');
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$server = Server::make()
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->setServerInfo('Cached Discovery Calculator', '1.0.0', 'Calculator with cached discovery for better performance.')
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->setContainer(container())
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->setLogger(logger())
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->setDiscovery(__DIR__, ['.'])
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->setCache(new Psr16Cache(new ArrayAdapter()))
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->build();
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$transport = new StdioTransport(logger: logger());
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$server->connect($transport);
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$transport->listen();
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logger()->info('Server listener stopped gracefully.');

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