public function __construct( $_id_or_email = false, $by_user_id = false ) {
    if ( false === $_id_or_email || ( is_numeric( $_id_or_email ) && absint( $_id_or_email ) !== (int) $_id_or_email ) ) {
      return false;
    }

    $by_user_id = is_bool( $by_user_id ) ? $by_user_id : false;

    if ( is_object( $_id_or_email ) ) {
      $customer = $_id_or_email;
    } else {
      if ( is_numeric( $_id_or_email ) ) {
        $field = $by_user_id ? 'user_id' : 'id';
      } else {
        $field = 'email';
      }

      $customer = edd_get_customer_by( $field, $_id_or_email );
    }

    if ( empty( $customer ) || ! is_object( $customer ) ) {
      return false;
    }

    $this->setup_customer( $customer );
  }