What are the benefits of using Dependency Injection over a Singleton pattern for managing database connections in PHP applications?

Using Dependency Injection over a Singleton pattern for managing database connections in PHP applications allows for better separation of concerns and easier testing. Dependency Injection promotes loose coupling between classes, making it easier to swap out different implementations of the database connection without changing the dependent classes. This approach also follows the principle of Dependency Inversion, where high-level modules do not depend on low-level modules directly, but instead both depend on abstractions. 

class DatabaseConnection {
    private $connection;

    public function __construct(PDO $connection) {
        $this->connection = $connection;
    }

    public function query($sql) {
        return $this->connection->query($sql);
    }
}

$pdo = new PDO('mysql:host=localhost;dbname=my_database', 'username', 'password');
$dbConnection = new DatabaseConnection($pdo);
$result = $dbConnection->query('SELECT * FROM users');

Keywords

Dependency Injection Singleton pattern database connections PHP applications benefits

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