PHP 프레임워크의 코드 리팩토링 및 디자인 패턴

function get_user_data($id) {
  $user = $this->db->query("SELECT * FROM users WHERE id = $id");
  if ($user->num_rows() > 0) {
    return $user->row_array();
  } else {
    return null;
  }
}

function get_user_data($id) {
  return $this->get_user($id);
}

private function get_user($id) {
  $user = $this->db->query("SELECT * FROM users WHERE id = $id");
  if ($user->num_rows() > 0) {
    return $user->row_array();
  } else {
    return null;
  }
}

class User {

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

  public function say_hello() {
    echo "Hello, my name is {$this->name}.";
  }
}

class User {

  private static $instance = null;

  private function __construct($name) {
    $this->name = $name;
  }

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

    return self::$instance;
  }

  public function say_hello() {
    echo "Hello, my name is {$this->name}.";
  }
}