<?php namespace DesignPatterns\Structural\DependencyInjection; class DatabaseConnection { /** * @var DatabaseConfiguration */ private $configuration; /** * @param DatabaseConfiguration $config */ public function __construct(DatabaseConfiguration $config) { $this->configuration = $config; } public function getDsn(): string { // this is just for the sake of demonstration, not a real DSN // notice that only the injected config is used here, so there is // a real separation of concerns here return sprintf( '%s:%s@%s:%d', $this->configuration->getUsername(), $this->configuration->getPassword(), $this->configuration->getHost(), $this->configuration->getPort() ); } }