Why doesn't XDebug work with Docker?

Question

xdebug

I want to set up locally Docker(WSL2) + VS Code + XDebug 3.
I googled and searched the forums, but this bundle does not work. Configs:
xdebug.ini

[XDebug]
xdebug.mode = develop
xdebug.start_with_request = yes
xdebug.client_host = host.docker.internal
xdebug.client_port = 9003

docker-compose.yml

version: '3'

networks:
  default:
    driver: bridge

services:

  frontend:
    build: frontend
    ports:
      - 20080:80
    volumes:
      # Re-use local composer cache via host-volume
      - ~/.composer-docker/cache:/root/.composer/cache:delegated
      # Mount source-code for development
      - ./:/app

  backend:
    build: backend
    ports:
      - 21080:80
    volumes:
      # Re-use local composer cache via host-volume
      - ~/.composer-docker/cache:/root/.composer/cache:delegated
      # Mount source-code for development
      - ./:/app

  php:
    image: yiisoftware/yii2-php:7.2-apache
    volumes:
      - ~/.composer-docker/cache:/root/.composer/cache:delegated
      - ./:/app:delegated
      - ./docker/php/xdebug.ini:/usr/local/etc/php/conf.d/xdebug.ini
      - ./docker/apache/000-default.conf:/etc/apache2/sites-available/000-default.conf
    environment:
      - PHP_ENABLE_XDEBUG=1
      - XDEBUG_CLIENT_PORT=9003
    ports:
      - '80:80'
    networks:
      - default
    depends_on:
      - db
  db:
    image: mysql:5.7.16
    restart: always
    environment:
      - MYSQL_DATABASE=yii2advanced
      - MYSQL_USER=user
      - MYSQL_PASSWORD=root
      - MYSQL_ROOT_PASSWORD=root
    ports:
      - '13306:3306'
    command: mysqld --sql_mode='' --character-set-server=utf8 --collation-server=utf8_general_ci
    volumes:
      - ./docker/mysql:/var/lib/mysql
    networks:
      - default
  phpmyadmin:
    image: phpmyadmin/phpmyadmin
    ports:
      - '8888:80'
    environment:
      - PMA_ARBITRARY=1
      - PMA_HOST=db
    depends_on:
      - db

launch.json

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Listen for XDebug",
            "type": "php",
            "request": "launch",
            "port": 9003,
            "pathMappings": {
                "app": "${workspaceFolder}"
            },
            "hostname": "localhost"
        }
    ]
}

Tell me, what could be the problem?

Answer 1

Most likely because port 9003 is not forwarded.
In the PHP section in the ports add
- '9003:9003'