Chapter 6: Client Communication: Sampling, Logging, and Progress

Welcome to Chapter 6: Client Communication: Sampling, Logging, and Progress. In this part of MCP PHP SDK Tutorial: Building MCP Servers in PHP with Discovery and Transport Flexibility, you will build an intuitive mental model first, then move into concrete implementation details and practical production tradeoffs.

This chapter explains server-to-client communication utilities in PHP MCP handlers.

Learning Goals

• use client gateway patterns for server-initiated communication
• apply sampling requests with clear user-control boundaries
• emit log and progress signals in protocol-compliant form
• reduce handler complexity around async-like notification flows

Communication Surface

Surface	Purpose
Sampling	server asks client to run model generation
Logging	structured diagnostics and observability
Progress	incremental status feedback for long-running calls
Notifications	out-of-band updates to client state

Source References

• Client Communication Guide
• MCP Elements Guide - Logging

Summary

You now have an operational communication model for richer PHP MCP server UX.

Next: Chapter 7: Framework Integration, Session Stores, and Dependencies

Source Code Walkthrough

examples/server/oauth-keycloak/keycloak/mcp-realm.json

The mcp-realm module in examples/server/oauth-keycloak/keycloak/mcp-realm.json handles a key part of this chapter's functionality:

{
  "realm": "mcp",
  "enabled": true,
  "registrationAllowed": false,
  "loginWithEmailAllowed": true,
  "duplicateEmailsAllowed": false,
  "resetPasswordAllowed": true,
  "editUsernameAllowed": false,
  "bruteForceProtected": true,
  "accessTokenLifespan": 300,
  "ssoSessionIdleTimeout": 1800,
  "ssoSessionMaxLifespan": 36000,
  "clients": [
    {
      "clientId": "mcp-client",
      "name": "MCP Client Application",
      "description": "Public client for MCP client applications",
      "enabled": true,
      "publicClient": true,
      "standardFlowEnabled": true,
      "directAccessGrantsEnabled": true,
      "serviceAccountsEnabled": false,
      "authorizationServicesEnabled": false,
      "fullScopeAllowed": true,
      "redirectUris": [
        "http://localhost:*",
        "http://127.0.0.1:*"
      ],
      "webOrigins": [
        "http://localhost:*",
        "http://127.0.0.1:*"
      ],
      "defaultClientScopes": [
        "openid",
        "profile",

This module is important because it defines how MCP PHP SDK Tutorial: Building MCP Servers in PHP with Discovery and Transport Flexibility implements the patterns covered in this chapter.

examples/server/oauth-microsoft/docker-compose.yml

The docker-compose module in examples/server/oauth-microsoft/docker-compose.yml handles a key part of this chapter's functionality:

services:
  php:
    build:
      context: .
      dockerfile: Dockerfile
    container_name: mcp-php-microsoft
    volumes:
      - ../../../:/app
    working_dir: /app
    env_file:
      - .env
    environment:
      AZURE_TENANT_ID: ${AZURE_TENANT_ID:-}
      AZURE_CLIENT_ID: ${AZURE_CLIENT_ID:-}
      AZURE_CLIENT_SECRET: ${AZURE_CLIENT_SECRET:-}
    command: >
      sh -c "mkdir -p /app/examples/server/oauth-microsoft/sessions;
      chmod -R 0777 /app/examples/server/oauth-microsoft/sessions;
      touch /app/examples/server/oauth-microsoft/dev.log;
      chmod 0666 /app/examples/server/oauth-microsoft/dev.log;
      touch /app/examples/server/dev.log;
      chmod 0666 /app/examples/server/dev.log;
      composer install --no-interaction --quiet 2>/dev/null || true;
      php-fpm"
    networks:
      - mcp-network

  nginx:
    image: nginx:alpine
    container_name: mcp-nginx-microsoft
    ports:
      - "${MCP_HTTP_PORT:-8000}:80"
    volumes:
      - ./nginx/default.conf:/etc/nginx/conf.d/default.conf:ro
      - ../../../:/app:ro

This module is important because it defines how MCP PHP SDK Tutorial: Building MCP Servers in PHP with Discovery and Transport Flexibility implements the patterns covered in this chapter.

composer.json

The composer module in composer.json handles a key part of this chapter's functionality:

{
  "name": "mcp/sdk",
  "description": "Model Context Protocol SDK for Client and Server applications in PHP",
  "license": "Apache-2.0",
  "type": "library",
  "authors": [
    {
      "name": "Christopher Hertel",
      "email": "mail@christopher-hertel.de"
    },
    {
      "name": "Kyrian Obikwelu",
      "email": "koshnawaza@gmail.com"
    },
    {
      "name": "Tobias Nyholm",
      "email": "tobias.nyholm@gmail.com"
    }
  ],
  "require": {
    "php": "^8.1",
    "ext-fileinfo": "*",
    "opis/json-schema": "^2.4",
    "php-http/discovery": "^1.20",
    "phpdocumentor/reflection-docblock": "^5.6 || ^6.0",
    "psr/clock": "^1.0",
    "psr/container": "^1.0 || ^2.0",
    "psr/event-dispatcher": "^1.0",
    "psr/http-client": "^1.0",
    "psr/http-factory": "^1.1",
    "psr/http-message": "^1.1 || ^2.0",
    "psr/http-server-handler": "^1.0",
    "psr/http-server-middleware": "^1.0",
    "psr/log": "^1.0 || ^2.0 || ^3.0",
    "symfony/finder": "^5.4 || ^6.4 || ^7.3 || ^8.0",

This module is important because it defines how MCP PHP SDK Tutorial: Building MCP Servers in PHP with Discovery and Transport Flexibility implements the patterns covered in this chapter.

How These Components Connect

flowchart TD
    A[mcp-realm]
    B[docker-compose]
    C[composer]
    A --> B
    B --> C