--- docker-compose.yml ---

    ...
    # NGINX
    nginx:
        build: ./containers/nginx
        container_name: nginx
        volumes_from:
            - volume_dckb
            - volume_log
        ports:
            - "8080:80"
        links:
            - php-fpm

    # PHP-FPM
    php-fpm:
        build: ./containers/php-fpm
        container_name: php-fpm
        volumes_from:
            - volume_dckb
        expose:
            - "9000"

    # PostgreSQL
    postgres:
        build: ./containers/postgres
        container_name: postgres
        volumes_from:
            - volume_data
        expose:
            - "5432"
        environment:
            POSTGRES_DB: homestead
            POSTGRES_USER: homestead
            POSTGRES_PASSWORD: secret
    ...

--- postgres/Dockerfile ---

FROM postgres:9.4.9

CMD ["postgres"]

EXPOSE 5432

--- php-fpm/Dockerfile ---

FROM php:7.0.9-fpm

RUN apt-get update && \
    apt-get install -y --no-install-recommends \
    libmcrypt-dev \
    libpq-dev

RUN docker-php-ext-install mcrypt
RUN docker-php-ext-install pdo_pgsql

RUN usermod -u 1000 www-data

WORKDIR /dckb

CMD ["php-fpm"]

EXPOSE 9000

--- index.php ---

<?php
try {
    $db = new PDO('pgsql:host=localhost;port=5432;dbname=homestead;user=homestead;password=secret');
} catch (PDOException $e) {
    print "ERROR: " . $e->getMessage() . "<br/>";
    die();
}
?>