싱글톤 패턴을 사용하여 PHP 클래스에서 데이터베이스 연결을 효과적으로 관리하는 방법은 무엇입니까?

<code class="php">class DatabaseConnection
{
    private static $instance;

    private function __construct()
    {
        // Connect to the database here
    }

    public static function getInstance()
    {
        if (self::$instance === null) {
            self::$instance = new DatabaseConnection();
        }

        return self::$instance;
    }

    public function prepare($query)
    {
        return self::$instance->prepare($query);
    }

    public function execute($query)
    {
        return self::$instance->execute($query);
    }
}</code>

<code class="php">class Foo
{
    public function bar()
    {
        $dbh = DatabaseConnection::getInstance();

        $stmt = $dbh->prepare('SELECT * FROM table');
        $stmt->execute();
    }
}</code>