Using Docker Compose for PHP and MySQL

Show how application code connects to the Compose database service over the private service network.

The objective is to understand the behavior and operational limits, not only the method name.

What It Does

Show how application code connects to the Compose database service over the private service network.

Prerequisites

Use a dedicated development environment and sample data. Where a snippet uses an injected connection, repository, request value or mailer, supply it from your own application setup.

Example 1: Basic Use

A focused working pattern for this topic. Names such as $pdo, $authContext and $repo represent dependencies provided by the application unless initialized in the snippet.

<?php
$db = new PDO('mysql:host=db;dbname=app;charset=utf8mb4', getenv('DB_USER'), getenv('DB_PASSWORD'));
$stmt = $db->query('SELECT NOW()');
echo $stmt->fetchColumn();

Example 2: A Second Scenario

A second use case that adds a different operation or data flow specific to this topic.

<?php
$db = new PDO('mysql:host=db;port=3306;dbname=app;charset=utf8mb4', getenv('DB_USER'), getenv('DB_PASSWORD'));
$result = $db->query('SELECT DATABASE()')->fetchColumn();
echo $result;

Example 3: Practical Checks

A practical validation, failure or deployment concern specific to this topic.

<?php
$host = getenv('DB_HOST') ?: 'db';
if ($host === '127.0.0.1') throw new RuntimeException('Separate containers cannot use loopback for service discovery');
$db = new PDO('mysql:host=' . $host . ';dbname=app;charset=utf8mb4', getenv('DB_USER'), getenv('DB_PASSWORD'));

Important Behavior and Edge Cases

The host name inside the PHP container is the Compose service name, not localhost.

For production use, also account for error handling, data validation, resource limits and environment-specific driver behavior.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Show how application code connects to the Compose database service over the private service network.
• The host name inside the PHP container is the Compose service name, not localhost.
• Use this workflow as a focused starting point rather than a substitute for application-level tests.

Choose this API or pattern when its exact semantics match your task, and verify the result against the database driver and runtime used by your application.