Managing Configuration with Environment Files

The Twelve-Factor App Approach

Configuration that varies between environments (development, staging, production) should be stored in environment variables, not in code.

.env Files

# .env
DATABASE_URL=mysql://user:pass@localhost/myapp
REDIS_URL=redis://localhost:6379
API_KEY=sk_live_abc123
DEBUG=false
LOG_LEVEL=warning

Loading in Different Languages

# PHP
$dotenv = parse_ini_file('.env');
# Or use vlucas/phpdotenv package

# Node.js (with dotenv package)
require('dotenv').config();
console.log(process.env.DATABASE_URL);

# Python (with python-dotenv)
from dotenv import load_dotenv
load_dotenv()
import os
db_url = os.getenv('DATABASE_URL')

Docker Compose

services:
  app:
    env_file:
      - .env
    # Or explicit:
    environment:
      - DATABASE_URL=${DATABASE_URL}

Security Rules

• Never commit .env to version control
• Add .env to .gitignore
• Provide .env.example with dummy values
• Use separate files per environment: .env.production, .env.staging
• Restrict file permissions: chmod 600 .env