# phpman > man > HTTP::Headers::Util(3pm)

## NAME
    [HTTP::Headers::Util](https://www.chedong.com/phpMan.php/perldoc/HTTP%3A%3AHeaders%3A%3AUtil/markdown) - Header value parsing utility functions

## VERSION
    version 6.36

## SYNOPSIS
      use [HTTP::Headers::Util](https://www.chedong.com/phpMan.php/perldoc/HTTP%3A%3AHeaders%3A%3AUtil/markdown) qw(split_header_words);
      @values = split_header_words($h->header("Content-Type"));

## DESCRIPTION
    This module provides a few functions that helps parsing and construction of valid HTTP header
    values. None of the functions are exported by default.

    The following functions are available:

### split_header_words
        This function will parse the header values given as argument into a list of anonymous arrays
        containing key/value pairs. The function knows how to deal with ",", ";" and "=" as well as
        quoted values after "=". A list of space separated tokens are parsed as if they were
        separated by ";".

        If the @header_values passed as argument contains multiple values, then they are treated as
        if they were a single value separated by comma ",".

        This means that this function is useful for parsing header fields that follow this syntax
        (BNF as from the HTTP/1.1 specification, but we relax the requirement for tokens).

          headers           = #header
          header            = (token | parameter) *( [";"] (token | parameter))

          token             = 1*<any CHAR except CTLs or separators>
          separators        = "(" | ")" | "<" | ">" | "@"
                            | "," | ";" | ":" | "\" | <">
                            | "/" | "[" | "]" | "?" | "="
                            | "{" | "}" | SP | HT

          quoted-string     = ( <"> *(qdtext | quoted-pair ) <"> )
          qdtext            = <any TEXT except <">>
          quoted-pair       = "\" CHAR

          parameter         = attribute "=" value
          attribute         = token
          value             = token | quoted-string

        Each *header* is represented by an anonymous array of key/value pairs. The keys will be all
        be forced to lower case. The value for a simple token (not part of a parameter) is "undef".
        Syntactically incorrect headers will not necessarily be parsed as you would want.

        This is easier to describe with some examples:

           split_header_words('foo="bar"; port="80,81"; DISCARD, BAR=baz');
           split_header_words('text/html; charset="iso-8859-1"');
           split_header_words('Basic realm="\\"foo\\\\bar\\""');

        will return

           [foo=>'bar', port=>'80,81', discard=> undef], [bar=>'baz' ]
           ['text/html' => undef, charset => 'iso-8859-1']
           [basic => undef, realm => "\"foo\\bar\""]

        If you don't want the function to convert tokens and attribute keys to lower case you can
        call it as "_split_header_words" instead (with a leading underscore).

### join_header_words
        This will do the opposite of the conversion done by split_header_words(). It takes a list of
        anonymous arrays as arguments (or a list of key/value pairs) and produces a single header
        value. Attribute values are quoted if needed.

        Example:

           join_header_words(["text/plain" => undef, charset => "iso-8859/1"]);
           join_header_words("text/plain" => undef, charset => "iso-8859/1");

        will both return the string:

           text/plain; charset="iso-8859/1"

## AUTHOR
    Gisle Aas <<gisle@activestate.com>>

## COPYRIGHT AND LICENSE
    This software is copyright (c) 1994 by Gisle Aas.

    This is free software; you can redistribute it and/or modify it under the same terms as the Perl
    5 programming language system itself.