NAME
    CGI::Header - Handle CGI.pm-compatible HTTP header properties

SYNOPSIS
      use CGI;
      use CGI::Header;

      my $query = CGI->new;

      # CGI.pm-compatible HTTP header properties
      my $header = CGI::Header->new(
          query => $query,
          header => {
              attachment => 'foo.gif',
              charset    => 'utf-7',
              cookies    => [ $cookie1, $cookie2 ], # CGI::Cookie objects
              expires    => '+3d',
              nph        => 1,
              p3p        => [qw/CAO DSP LAW CURa/],
              target     => 'ResultsWindow',
              type       => 'image/gif'
          },
      );

      # update $header
      $header->set( 'Content-Length' => 3002 ); # overwrite
      $header->delete('Content-Disposition'); # => 3002
      $header->clear; # => $self

      $header->as_string; # => "Content-Type: text/html\n..."

VERSION
    This document refers to CGI::Header version 0.51.

DEPENDENCIES
    This module is compatible with CGI.pm 3.51 or higher.

DESCRIPTION
    This module is a utility class to manipulate a hash reference received
    by CGI.pm's "header()" method.

    This module isn't the replacement of the "header()" method, but
    complements CGI.pm.

    This module can be used in the following situation:

    1. $header is a hash reference which represents CGI response headers
        For example, CGI::Application implements "header_add()" method which
        can be used to add CGI.pm-compatible HTTP header properties.
        Instances of CGI.pm-based applications often hold those properties.

          my $header = { type => 'text/plain' };

    2. Manipulates $header using CGI::Header
        Since property names are case-insensitive, application developers
        have to normalize them manually when they specify header properties.
        CGI::Header normalizes them automatically.

          use CGI::Header;

          my $h = CGI::Header->new( header => $header );
          $h->set( 'Content-Length' => 3002 ); # add Content-Length header

          $header;
          # => {
          #     'type' => 'text/plain',
          #     'content-length' => '3002',
          # }

    3. Passes $header to CGI::header() to stringify the variable
          use CGI;

          print CGI::header( $header );
          # Content-length: 3002
          # Content-Type: text/plain; charset=ISO-8859-1
          #

        "header()" function just stringifies given header properties. This
        module can be used to generate PSGI-compatible response header array
        references. See CGI::Header::PSGI.

  ATTRIBUTES
    $header->query
        Returns your current query object. This attribute defaults to the
        Singleton instance of CGI.pm ($CGI::Q), which is shared by functions
        exported by the module.

    $hashref = $header->header
        Returns the header hash reference associated with this CGI::Header
        object. This attribute defaults to a reference to an empty hash. The
        hashref will be passed to CGI.pm's "header" method to generate CGI
        response headers. See "CGI::Header#as_string".

  METHODS
    $value = $header->get( $field )
    $value = $header->set( $field => $value )
        Get or set the value of the header field. The header field name
        ($field) is not case sensitive.

          # field names are case-insensitive
          $header->get('Content-Length');
          $header->get('content-length');

        The $value argument must be a plain string:

          $header->set( 'Content-Length' => 3002 );
          my $length = $header->get('Content-Length'); # => 3002

    $bool = $header->exists( $field )
        Returns a Boolean value telling whether the specified field exists.

          if ( $header->exists('ETag') ) {
              ...
          }

    $value = $header->delete( $field )
        Deletes the specified field form CGI response headers. Returns the
        value of the deleted field.

          my $value = $header->delete('Content-Disposition'); # => 'inline'

    $self = $header->clear
        This will remove all header properties.

    $header->as_string
        It's identical to:

          $header->query->header( $header->header );

  PROPERTIES
    The following methods were named after property names recognized by
    CGI.pm's "header" method. Most of these methods can both be used to read
    and to set the value of a property.

    If you pass an argument to the method, the property value will be set,
    and also the current object itself will be returned; therefore you can
    chain methods as follows:

      $header->type('text/html')->charset('utf-8');

    If no argument is supplied, the property value will be returned. If the
    given property doesn't exist, "undef" will be returned.

    $self = $header->attachment( $filename )
    $filename = $header->attachment
        Get or set the "attachment" property. Can be used to turn the page
        into an attachment. Represents suggested name for the saved file.

          $header->attachment('genome.jpg');

        In this case, the outgoing header will be formatted as:

          Content-Disposition: attachment; filename="genome.jpg"

    $self = $header->charset( $character_set )
    $character_set = $header->charset
        Get or set the "charset" property. Represents the character set sent
        to the browser.

    $self = $header->cookies([ $cookie1, $cookie2, ... ])
    $cookies = $header->cookies
        Get or set the "cookies" property.

    $self = $header->expires( $format )
    $format = $header->expires
        Get or set the "expires" property. The Expires header gives the date
        and time after which the entity should be considered stale. You can
        specify an absolute or relative expiration interval. The following
        forms are all valid for this field:

          $header->expires( '+30s' ); # 30 seconds from now
          $header->expires( '+10m' ); # ten minutes from now
          $header->expires( '+1h'  ); # one hour from now
          $header->expires( 'now'  ); # immediately
          $header->expires( '+3M'  ); # in three months
          $header->expires( '+10y' ); # in ten years time

          # at the indicated time & date
          $header->expires( 'Thu, 25 Apr 1999 00:40:33 GMT' );

    $self = $header->location( $url )
    $url = $header->location
        Get or set the Location header.

          $header->location('http://somewhere.else/in/movie/land');

    $self = $header->nph( $bool )
    $bool = $header->nph
        Get or set the "nph" property. If set to a true value, will issue
        the correct headers to work with a NPH (no-parse-header) script.

          $header->nph(1);

    $tags = $header->p3p
    $self = $header->p3p( $tags )
        Get or set the "p3p" property. The parameter can be an arrayref or a
        space-delimited string.

          $header->p3p([qw/CAO DSP LAW CURa/]);
          # or
          $header->p3p('CAO DSP LAW CURa');

        In this case, the outgoing header will be formatted as:

          P3P: policyref="/w3c/p3p.xml", CP="CAO DSP LAW CURa"

    $self = $header->redirect( $url[, $status] );
        Sets redirect URL with an optional status code and a human-readable
        message, which defaults to "302 Found". Returns this object itself.

          $header->redirect('http://somewhere.else/in/movie/land');

    $self = $header->status( $status )
    $status = $header->status
        Get or set the Status header.

          $header->status('304 Not Modified');

    $self = $header->target( $window_target )
    $window_target = $header->target
        Get or set the Window-Target header.

          $header->target('ResultsWindow');

    $self = $header->type( $media_type )
    $media_type = $header->type
        Get or set the "type" property. Represents the media type of the
        message content.

          $header->type('text/html');

  NORMALIZING PROPERTY NAMES
    This class normalizes property names automatically. Normalized property
    names are:

    1. lowercased
          'Content-Length' -> 'content-length'

    2. use dashes instead of underscores in property name
          'content_length' -> 'content-length'

    CGI.pm's "header" method also accepts aliases of property names. This
    module converts them as follows:

     'content-type'  -> 'type'
     'cookie'        -> 'cookies'
     'set-cookie'    -> 'cookies'
     'window-target' -> 'target'

    If a property name is duplicated, throws an exception:

      my $header = CGI::Header->new(
          header => {
              -Type        => 'text/plain',
              Content_Type => 'text/html',
          }
      );
      # die "Property '-type' already exists"

EXAMPLES
  WRITING Blosxom PLUGINS
    The following plugin just adds the Content-Length header to CGI response
    headers sent by blosxom.cgi:

      package content_length;
      use CGI::Header;

      sub start {
          !$blosxom::static_entries;
      }

      sub last {
          my $h = CGI::Header->new( header => $blosxom::header )->rehash;
          $h->set( 'Content-Length' => length $blosxom::output );
      }

      1;

    Since Blosxom <http://blosxom.sourceforge.net/> depends on the
    procedural interface of CGI.pm, you don't have to pass $query to "new()"
    in this case.

  HANDLING HTTP COOKIES
    It's up to you to decide how to manage HTTP cookies.

      use parent 'CGI::Header';

      # Add cookie() attribute which defaults a reference to an empty hash.
      # The keys of the hash are the cookies' names, and their corresponding
      # values are a plain string, e.g., "$header->cookie->{ID} = 123456"
      sub cookie {
          $_[0]->{cookie} ||= {};
      }

      # The 'cookies' property defaults to an arrayref
      sub cookies {
          $_[0]->header->{cookies} ||= [];
      }

      # Override as_string() to create and set CGI::Cookie objects right before
      # stringifying header props.
      sub as_string {
          my $self    = shift;
          my $query   = $self->query;
          my $cookies = $self->cookies;

          while ( my ($name, $value) = each %{$self->cookie} ) {
              push @{$cookies}, $query->cookie( $name => $value );
          }

          $self->SUPER::as_string;
      }

  WORKING WITH CGI::Simple
    Since CGI::Simple is "a relatively lightweight drop in replacement for
    CGI.pm", this module is compatible with the module. If you're using the
    procedural interface of the module (CGI::Simple::Standard), you need to
    override the "_build_query" method as follows:

      use parent 'CGI::Header';
      use CGI::Simple::Standard;

      sub _build_query {
          # NOTE: loader() is designed for debugging
          CGI::Simple::Standard->loader('_cgi_object');
      }

LIMITATIONS
    Since the following strings conflict with property names, you can't use
    them as field names ($field):

      "Attachment"
      "Charset"
      "Cookie"
      "Cookies"
      "NPH"
      "Target"
      "Type"

    Content-Type
        If you don't want to send the Content-Type header, set the "type"
        property to an empty string, though it's far from intuitive
        manipulation:

          $header->type(q{});

          # doesn't work as you expect
          $header->delete('Content-Type');
          $header->type(undef);

    Date
        If one of the following conditions is met, the Date header will be
        set automatically, and also the header field will become read-only:

          if ( $header->nph or $header->cookie or $header->expires ) {
              $header->set( 'Date' => 'Thu, 25 Apr 1999 00:40:33 GMT' ); # wrong
              $header->delete('Date'); # wrong
          }

    P3P You can't assign to the P3P header directly:

          # wrong
          $header->set( 'P3P' => '/path/to/p3p.xml' );

        "CGI::header()" restricts where the policy-reference file is
        located, and so you can't modify the location ("/w3c/p3p.xml").
        You're allowed to set P3P tags using "p3p()".

    Pragma
        If the following condition is met, the Pragma header will be set
        automatically, and also the header field will become read-only:

          if ( $header->query->cache ) {
              $header->set( 'Pragma' => 'no-cache' ); # wrong
              $header->delete('Pragma'); # wrong
          }

    Server
        If the following condition is met, the Server header will be set
        automatically, and also the header field will become read-only:

          if ( $header->nph ) {
              $header->set( 'Server' => 'Apache/1.3.27 (Unix)' ); # wrong
              $header->delete('Server'); # wrong
          }

SEE ALSO
    CGI, HTTP::Headers

BUGS
    There are no known bugs in this module. Please report problems to
    ANAZAWA (anazawa@cpan.org). Patches are welcome.

AUTHOR
    Ryo Anazawa (anazawa@cpan.org)

LICENSE
    This module is free software; you can redistibute it and/or modify it
    under the same terms as Perl itself. See perlartistic.