protected function validateColumns( $columns )
    {
        $patterns = array(
            '((?P<minute>(?:\*|(?:(?:[0-9]|[1-5][0-9])(?:-(?:[0-9]|[1-5][0-9]))?)(?:,(?:[0-9]|[1-5][0-9])(?:-(?:[0-9]|[1-5][0-9]))?)*)(?:/(?:[1-9]|[1-5][0-9]))?)$)AD',
            '((?P<hour>(?:\*|(?:(?:[0-9]|1[0-9]|2[0-3])(?:-(?:[0-9]|1[0-9]|2[0-3]))?)(?:,(?:[0-9]|1[0-9]|2[0-3])(?:-(?:[0-9]|1[0-9]|2[0-3]))?)*)(?:/(?:[1-9]|1[0-9]|2[0-3]))?)$)AD',
            '((?P<dayOfMonth>(?:\*|(?:(?:[1-9]|[1-2][0-9]|3[0-1])(?:-(?:[1-9]|[1-2][0-9]|3[0-1]))?)(?:,(?:[1-9]|[1-2][0-9]|3[0-1])(?:-(?:[1-9]|[1-2][0-9]|3[0-1]))?)*)(?:/(?:[1-9]|[1-2][0-9]|3[0-1]))?)$)AD',
            '((?P<month>(?:\*|(?:(?:[1-9]|1[0-2])(?:-(?:[1-9]|1[1-2]))?)(?:,(?:[1-9]|1[1-2])(?:-(?:[1-9]|1[1-2]))?)*)(?:/(?:[1-9]|1[1-2]))?)$)AD',
            '((?P<dayOfWeek>(?:\*|(?:(?:[0-7])(?:-(?:[0-7]))?)(?:,(?:[0-7])(?:-(?:[0-7]))?)*)(?:/(?:[1-7]))?)$)AD',
        );

        if ( count( $columns ) !== 5 )
        {
            return false;
        }

        foreach( $columns as $key => $column )
        {
            if ( preg_match( $patterns[$key], $column ) !== 1 )
            {
                return (int)$key;
            }
        }

        return true;
    }