90-xdebug.ini

xdebug.mode=debug
xdebug.discover_client_host=0
xdebug.client_host=host.docker.internal

arquivo.php

<?php

function exibeMensagem(string $texto): void
{
    echo $texto;
}

$texto = 'Olá mundo';

exibeMensagem($texto);

docker-compose.yaml

version: '3.7'
services:
  php:
    build:
      context: .
    extra_hosts:
      - "host.docker.internal:host-gateway"
    ports:
      - 8123:8123
    volumes:
      - ./:/app
    working_dir: /app
    entrypoint: "php -S 0.0.0.0:8123"

Dockerfile

FROM php:8.1-cli

COPY 90-xdebug.ini "${PHP_INI_DIR}/conf.d"
RUN pecl install xdebug
RUN docker-php-ext-enable xdebug