各位开发者，我已经解决了最初的问题，但如果有人有一个可以运行这个的docker镜像，我会非常感激。我需要一个非常老的应用程序的帮助。
我正在为旧应用程序设置VM环境。如果您想提供帮助，请仔细阅读。
我有一个旧的应用程序，很快就会被扔掉，因为我们正在重写工作，但旧的应用程序仍然需要支持，它运行非常旧的PHP和MYSQL版本。下面的代码应该测试数据库连接是否正常工作。

require_once("/var/www/html/class/autoload.php");
$database = $_ENV['DB_HOST'];
$DBuser = $_ENV["MYSQL_USER"];
$DBpass = $_ENV["MYSQL_USER"];
$link = mysql_connect($database, $DBuser, $DBpass, null);

if (!$link) {
    echo "Error: Unable to connect to MySQL." . PHP_EOL;
    echo "Debugging errno: " . mysql_error() . PHP_EOL;
    exit;
}

密码破解了

Warning: mysql_connect(): No such file or directory in /var/www/html/docker_build/test_db.php on line 10
Error: Unable to connect to MySQL. Debugging errno: No such file or directory

如果在同一个代码块中我使用mysqli_connect istead，则一切正常，但项目运行在mysql_functions上。该应用程序在暂存和生产服务器上工作，我试图复制我的虚拟机上的设置，这里也是曾经工作的dockerfile，但最近一些安全更新阻止了它的工作。

version: "3"

services:
  webserver:
    build: 
      context: ${DOCKER_BUILD_ROOT}/bin/${DOCKER_PHPVERSION}
    container_name: ${DOCKER_PHPVERSION}
    restart: 'always'
    ports:
      - "${HOST_MACHINE_UNSECURE_HOST_PORT}:80"
      - "${HOST_MACHINE_SECURE_HOST_PORT}:443"
    links: 
      - database
    volumes: 
      - ${DOCUMENT_ROOT-.}:/var/www/html
      - ${PHP_INI-./docker_build/config/php/php.ini}:/usr/local/etc/php/php.ini
      - ${VHOSTS_DIR-./docker_build/config/vhosts}:/etc/apache2/sites-enabled
      - ${APACHE_LOG_DIR-./docker_build/logs/apache2}:/var/log/apache2
    # user: "1000:1000"
    user: root
  database:
    build:
      context: "${DOCKER_BUILD_ROOT}/bin/${DOCKER_DATABASE}"
    container_name: 'database'
    restart: 'always'
    ports:
      - "${DOCKER_LOCALHOST}:${HOST_MACHINE_MYSQL_PORT}:3306"
    volumes: 
      - ${MYSQL_CONF_FILE-./docker_build/config/mysql/mysql.conf.d/mysqld.cnf}:/etc/mysql/mysql.conf.d/mysqld.cnf
      - ${MYSQL_DATA_DIR-./docker_build/data/mysql}:/var/lib/mysql
      - ${MYSQL_LOG_DIR-./docker_build/logs/mysql}:/var/log/mysql
      - ${MYSQL_INIT_DIR-./docker_build/config/mysql/ini}:/docker-entrypoint-initdb.d
    environment:
      MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
      MYSQL_DATABASE: ${MYSQL_DATABASE}
      MYSQL_USER: ${MYSQL_USER}
      MYSQL_PASSWORD: ${MYSQL_PASSWORD}
  phpmyadmin:
    image: phpmyadmin/phpmyadmin
    container_name: 'phpmyadmin'
    links:
      - database
    environment:
      PMA_HOST: database
      PMA_PORT: 3306
      PMA_USER: ${MYSQL_USER}
      PMA_PASSWORD: ${MYSQL_PASSWORD}
      MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
      MYSQL_USER: ${MYSQL_USER}
      MYSQL_PASSWORD: ${MYSQL_PASSWORD}
    ports:
      - '8080:80'
    volumes: 
      - /sessions
      - ${PHP_INI-./docker_build/config/php/php.ini}:/usr/local/etc/php/conf.d/php-phpmyadmin.ini
  redis:
    container_name: 'redis'
    image: redis:latest
    ports:
      - "${DOCKER_LOCALHOST}:${HOST_MACHINE_REDIS_PORT}:6380"

FROM php:5.6-apache

RUN apt-get -y update && apt-get upgrade -y

# Install tools && libraries
RUN apt-get -y install --fix-missing apt-utils nano wget dialog \
    build-essential git curl libcurl3 libcurl3-dev zip \
    libmcrypt-dev libsqlite3-dev libsqlite3-0 mysql-client \
    zlib1g-dev libicu-dev libfreetype6-dev libjpeg62-turbo-dev libpng-dev \
    && rm -rf /var/lib/apt/lists/*

# Composer
RUN curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer

# PHP5 Extensions

RUN docker-php-ext-install curl \
    && docker-php-ext-install tokenizer \
    && docker-php-ext-install json \
    && docker-php-ext-install mcrypt \
    && docker-php-ext-install pdo_mysql \
    && docker-php-ext-install pdo_sqlite \
    && docker-php-ext-install mysql \
    && docker-php-ext-install mysqli \
    && docker-php-ext-install zip \
    && docker-php-ext-install -j$(nproc) intl \
    && docker-php-ext-install mbstring \
    && docker-php-ext-configure gd --with-freetype-dir=/usr/include/ --with-jpeg-dir=/usr/include/ \
    && docker-php-ext-install -j$(nproc) gd \
    && pecl install xdebug-2.5.5 && docker-php-ext-enable xdebug

# Enable apache modules
RUN a2enmod rewrite headers

RUN apt-get update && apt-get install -y \
    mediainfo \
    jhead \
    imagemagick \
    ffmpeg

RUN usermod -u 1000 www-data

EXPOSE 80

# initialize server script. designed to be run after volumes are mounted.
# runs composer install and runs apache2 foreground.
# ENTRYPOINT ["/usr/sbin/apache2ctl", "-D", "FOREGROUND"]
ENTRYPOINT ["./docker_build/config/server_ini.sh"]

我只需要让它运行起来。如果它可以用docker来完成，那就太完美了，但我认为这个图像早就被弃用了。任何帮助都非常感谢。我可以为您提供env和.ini设置。我不想在这个问题上问得太多。
我尝试了所有的方法，我看了.ini和.env以及所有的Linux设置。看起来像mysql套接字没有正确设置，但是cmd连接工作正常mysql -uroot -p工作正常