original_string: public static function lower(string $str, string $encoding = null) : string
      {
          return mb_strtolower($str, $encoding ?: utils\Str::encoding($str));
      }
code: public static function lower(string $str, string $encoding = null) : string
      {
          return mb_strtolower($str, $encoding ?: utils\Str::encoding($str));
      }
code_tokens: public static function lower ( string $ str , string $ encoding = null ) : string { return mb_strtolower ( $ str , $ encoding ? : utils \ Str :: encoding ( $ str ) ) ; }
docstring: Converts all characters in the given string to lowercase.
  
  @param   string      $str        The string to convert.
  @param   string|null $encoding   The encoding to use.
  @return  string                  The converted string.
docstring_tokens: Converts all characters in the given string to lowercase .