code: public function bindColumn($column, &$value, $dataType = null)
      {
          if ($dataType === null) {
              $this->_statement->bindColumn($column, $value);
          } else {
              $this->_statement->bindColumn($column, $value, $dataType);
          }
      }
docs: Binds a column to a PHP variable.
  When rows of data are being fetched, the corresponding column value
  will be set in the variable. Note, the fetch mode must include PDO::FETCH_BOUND.
  @param int|string $column Number of the column (1-indexed) or name of the column
  in the result set. If using the column name, be aware that the name
  should match the case of the column, as returned by the driver.
  @param mixed $value Name of the PHP variable to which the column will be bound.
  @param int $dataType Data type of the parameter
  @see https://secure.php.net/manual/en/function.PDOStatement-bindColumn.php