Best Practices for Building and Deploying Apps with Docker

To dockerize a PHP form application and link it to a MySQL database, there are several steps you would need to take. This guide will also include the use of Docker Compose for easier orchestration of multi-container applications, data persistence, and Apache as the web server.

I am using a Mac Operating System (OS), feel free to use any other OS.

Prerequisite

Before reading this article, ensure you have knowledge of how Docker and docker-compose work.

Step 1: Create the PHP Application with a MySQL backend

Guide

<?php   
$host = "db";
$db_name = "test_db";
$username = "root";
$password = getenv('MYSQL_ROOT_PASSWORD');

try{
$connection = new PDO("mysql:host=" . $host . ";dbname=" . $db_name, $username, $password);
$connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); #enabled error reporting via PDOexceptions
$connection->exec("set names utf8");
}catch(Exception $exception){
echo "Connection error: " . $exception->getMessage();
}

function saveData($name, $email, $message){
global $connection;
$query = "INSERT INTO users(name, email, message) VALUES( :name, :email, :message)";

$callToDb = $connection->prepare( $query );
$name=htmlspecialchars(strip_tags($name));
$email=htmlspecialchars(strip_tags($email));
$message=htmlspecialchars(strip_tags($message));
$callToDb->bindParam(":name",$name);
$callToDb->bindParam(":email",$email);
$callToDb->bindParam(":message",$message);

if($callToDb->execute()){
return '<h3 style="text-align:center;">Saved to DB!</h3>';
}
}

if( isset($_POST['submit'])){
$name = htmlentities($_POST['name']);
$email = htmlentities($_POST['email']);
$message = htmlentities($_POST['message']);

// then you can use them in a PHP function. 
$result = saveData($name, $email, $message);
echo $result;
}
else{
echo '<h3 style="text-align:center;">A very detailed error message ( ͡° ͜ʖ ͡°)</h3>';
}
?>

index.php

<head>
    <title>
    Form
    </title>
    </head>
    <body>
    <form action="index.php" class="alt" method="POST">
    <div class="row uniform">
    <div class="name">
    <input name="name" id="" placeholder="Name" type="text">
    </div>
    <div class="email">
    <input name="email" placeholder="Email" type="email">
    </div>
    <div class="message">
    <textarea name="message" placeholder="Message" rows="4"></textarea>
    </div>
    </div>
    <br/>
    <input class="alt" value="Submit" name="submit" type="submit">
    </form>
    </body>

index.html

MYSQL_ROOT_PASSWORD=<some-value>
MYSQL_PASSWORD=<some-value>
DB_HOST=db
DB_PORT=3306
MYSQL_DATABASE=<some-value>
MYSQL_PORT=3306

.env

CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(255) NOT NULL,
    email VARCHAR(255) NOT NULL,
    message TEXT NOT NULL
);

main.sql

Step 2: Create Docker and Docker-compose files

FROM php:7.4-apache

# Install PDO MySQL extension
RUN docker-php-ext-install pdo_mysql

Dockerfile - by default, Apache exposes port 80; hence no need to add the code block EXPOSE 80

version: '3.8'
services:
  web:
      build: 
        context: .
        dockerfile: Dockerfile
      ports:
        - "8080:80"
      env_file:
        - .env
      volumes:
        - .:/var/www/html #to persist and kep track of changes to the code
      depends_on:
        - db

  db:
    image: mysql:latest
    command: --default-authentication-plugin=mysql_native_password
    restart: always
    env_file:
      - .env
    environment:
      MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
      MYSQL_DATABASE: ${MYSQL_DATABASE}
      MYSQL_USER: ${MYSQL_USER}
      MYSQL_PASSWORD: ${MYSQL_PASSWORD}
    ports:
      - 3306:3306
    healthcheck:
      test: ["CMD", "mysqladmin", "ping", "-h", "db"]
      interval: 20s
      timeout: 10s
      retries: 10
    volumes:
      - db_data:/var/lib/mysql
      - ./main.sql:/docker-entrypoint-initdb.d/main.sql #run the main.sql script upon startup

  phpmyadmin:
    image: phpmyadmin:latest
    ports:
        - '80:80'
    restart: always
    environment:
        PMA_HOST: db
    depends_on:
        - db

volumes:
  db_data:

networks:
  app-network:

docker-compose.yaml

Notes:

The volumes code block, persists data in the container, such that when the container is stopped and restarted, you will still have your database entries intact.
The healthcheck, ensures the MySQL service is fully ready before the web service tries to connect.
Since I did not specify a network driver, my containers, by default are connected to docker's bridge network. Bridge networks are usually used when your applications run in standalone containers that need to communicate.
To get the main.sql executed in the MySQL container, you have to delete any existing volumes in the container.

Step 3: Build and run the Docker application

$ docker-compose up --build

Testing the App

Head over to localhost:80, to access phpMyAdmin - to get a visual of your MySQL database*.* Sign in using the values of these variables: MYSQL_ROOT_PASSWORD and MYSQL_USER (.env file).
To access the application, head to localhost:8080/index.html, upon filling out the form, you will be redirected.

Log into phpMySQL, to get a visual of the data you just filled into the form.

Best Practices Used

Implement error handling in the PHP app.
Add a health check to the Docker compose file.
Mount a migration file that creates the database table on the MySQL container.
Create a docker ignore file .dockerignore .
```
  .git
  .gitignore
  .DS_Store
```

Create a git ignore file .gitignore.

  mysql_password.txt
  mysql_root_password.txt
  *.log
  .DS_Store
  .env

Store sensitive information as environment variables or use docker secrets (used with Docker swarm).

Repository

I hope this helps.

Goodluck 🫡

Efficient Containerization: A Comprehensive Guide to Building and Deploying Secure PHP-MySQL Web Applications with Docker

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