protected function getColumnIndex($field, string $error_message)
    {
        $method = is_string($field) ? 'getColumnIndexByValue' : 'getColumnIndexByKey';

        return $this->$method($field, $error_message);
    }
protected function getColumnIndex($field, string $error_message)
    {
        $method = is_string($field) ? 'getColumnIndexByValue' : 'getColumnIndexByKey';

        return $this->$method($field, $error_message);
    }
protected function getColumnIndex ( $ field , string $ error_message ) { $ method = is_string ( $ field ) ? 'getColumnIndexByValue' : 'getColumnIndexByKey' ; return $ this -> $ method ( $ field , $ error_message ) ; }
Filter a column name against the header if any.

@param string|int $field         the field name or the field index
@param string     $error_message the associated error message

@return string|int
Filter a column name against the header if any .