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Ryo Anazawa > CGI-Header-0.07 > CGI::Header



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Module Version: 0.07   Source   Latest Release: CGI-Header-0.63


CGI::Header - Adapter for CGI::header() function


  use CGI::Header;

  my $header = {
      -attachment => 'foo.gif',
      -charset    => 'utf-7',
      -cookie     => [ $cookie1, $cookie2 ], # CGI::Cookie objects
      -expires    => '+3d',
      -nph        => 1,
      -p3p        => [qw/CAO DSP LAW CURa/],
      -target     => 'ResultsWindow',
      -type       => 'image/gif',

  my $h = CGI::Header->new( $header );

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

  my @headers = $h->flatten;
  # => ( 'Content-length', '3002', 'Content-Type', 'text/plain' )

  print $h->as_string;
  # Content-length: 3002
  # Content-Type: text/plain

  $h->header; # same reference as $header


This module is a utility class to manipulate a hash reference which CGI's header() function receives. This class is, so to speak, a subclass of Hash because the function behaves like a hash, while Perl5 doesn't provide a built-in class called Hash.

This module isn't the replacement of the function. Although this class implements as_string() method, the function should stringify the reference in most cases.

The following use case is expected:

1. $header is a hash reference which represents CGI response headers
  my $header = { -type => 'text/plain' };
2. Manipulates $header using CGI::Header
  use CGI::Header;

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

  # => {
  #     -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 = CGI::Header->new({ -type => 'text/plain', ... })

Given a header hash reference, returns a CGI::Header object which holds a reference to the original given argument:

  my $header = { -type => 'text/plain' };
  my $h = CGI::Header->new( $header );

The object updates the reference when called write methods like set(), delete() or clear():

  # updates $header
  $h->set( 'Content-Length' => 3002 );
  $h->delete( 'Content-Disposition' );

It also has header() method that would return the same reference:

  $h->header; # same reference as $header
$header = CGI::Header->new( -type => 'text/plain', ... )

A shortcut for:

  my $header = CGI::Header->new({ -type => 'text/plain', ... });



Rebuilds the header hash to normalize parameter names without changing the reference:

  my $h1 = $header->header;
  # => {
  #     '-content_type' => 'text/plain',
  #     'Set-Cookie'    => 'ID=123456; path=/',
  #     'expires'       => '+3d',
  #     '-target'       => 'ResultsWindow',
  # }


  my $h2 = $header->header; # same reference as $h1
  # => {
  #     '-type'    => 'text/plain',
  #     '-cookie'  => 'ID=123456; path=/',
  #     '-expires' => '+3d',
  #     '-target'  => 'ResultsWindow',
  # }

If parameter names aren't normalized, the methods listed below won't work as you expect.

$value = $header->get( $field )
$header->set( $field => $value )

Get or set the value of the header field. The header field name ($field) is not case sensitive. You can use underscores as a replacement for dashes in header names.

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

The $value argument may be a plain string or a reference to an array of CGI::Cookie objects for the Set-Cookie header.

  $header->set( 'Content-Length' => 3002 );
  $header->set( 'Set-Cookie' => [$cookie1, $cookie2] );
$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'
@fields = $header->field_names

Returns the list of distinct field names present in the header. The field names have case as returned by CGI::header().

  my @fields = $header->field_names;
  # => ( 'Set-Cookie', 'Content-length', 'Content-Type' )
$header->each( \&callback )

Apply a subroutine to each header field in turn. The callback routine is called with two parameters; the name of the field and a value. If the Set-Cookie header is multi-valued, then the routine is called once for each value. Any return values of the callback routine are ignored.

  my @lines;

  $header->each(sub {
      my ( $field, $value ) = @_;
      push @lines, "$field: $value";

  print join @lines, "\n";
  # Content-length: 3002
  # Content-Type: text/plain
@headers = $header->flatten

Returns pairs of fields and values.

  @headers = $header->flatten;
  # => ( 'Content-length', '3002', 'Content-Type', 'text/plain' )

It's identical to:

  my @headers;
  $self->each(sub {
      my ( $field, $value ) = @_;
      push @headers, $field, "$value"; # force stringification

This method can be used to generate PSGI-compatible header array references:

  my $status_code = $header->delete( 'Status' ) || '200 OK';
  $status_code =~ s/\D*$//;

  $header->nph( 0 ); # removes the Server header

  my @headers = $header->flatten;

See also CGI::Emulate::PSGI, CGI::PSGI.


This will remove all header fields.

$bool = $header->is_empty

Returns true if the header contains no key-value pairs.


  if ( $header->is_empty ) { # true
$clone = $header->clone

Returns a copy of this CGI::Header object. It's identical to:

  my %copy = %{ $header->header };
  my $clone = CGI::Header->new( \%copy );
$header->as_string( $eol )

Returns the header fields as a formatted MIME header. The optional $eol parameter specifies the line ending sequence to use. The default is \015\012.

The following:

  use CGI;
  print CGI::header( $header->header );

is identical to:

  my $CRLF = $CGI::CRLF;
  print $header->as_string( $CRLF ), $CRLF;

When valid multi-line headers are included, this method will always output them back as a single line, according to the folding rules of RFC 2616: the newlines will be removed, while the white space remains.

Unlike, when invalid newlines are included, this module removes them instead of throwing exceptions.

$filename = $header->attachment
$header->attachment( $filename )

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"
@tags = $header->p3p_tags
$header->p3p_tags( @tags )

Represents P3P tags. The parameter can be an array or a space-delimited string. Returns a list of P3P tags.

  $header->p3p_tags(qw/CAO DSP LAW CURa/);

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

  P3P: policyref="/w3c/p3p.xml", CP="CAO DSP LAW CURa"
$format = $header->expires
$header->expires( $format )

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' );

If set to a true value, will issue the correct headers to work with a NPH (no-parse-header) script.

  $header->nph( 1 );


  use CGI::Header;

  my $header = { -type => 'text/plain' };
  tie my %header => 'CGI::Header' => $header;

  # update $header
  $header{'Content-Length'} = 3002;
  delete $header{'Content-Disposition'};
  %header = ();

Above methods are aliased as follows:

  TIEHASH -> new
  FETCH   -> get
  STORE   -> set
  DELETE  -> delete
  CLEAR   -> clear
  EXISTS  -> exists
  SCALAR  -> !is_empty

FIRSTKEY() and NEXTKEY() aren't implemented, and so you can't iterate through the tied hash.

  # doesn't work
  keys %header;
  values %header;
  each %header;

See also perltie.


Can't set '-content_type' to neither undef nor an empty string
  # wrong
  $header->set( 'Content-Type' => undef );
  $header->set( 'Content-Type' => q{} );

Use delete() instead:

  $header->delete( 'Content-Type' );
Can't assign to '-expires' directly, use expires() instead
  # wrong
  $header->set( 'Expires' => '+3d' );

Use expires() instead:

  $header->expires( '+3d' );

because the following behavior will surprize us:

  $header->set( 'Expires' => '+3d' );

  my $value = $header->get( 'Expires' );
  # => "Thu, 25 Apr 1999 00:40:33 GMT"
Can't assign to '-p3p' directly, use p3p_tags() instead

CGI::header() restricts where the policy-reference file is located, and so you can't modify the location (/w3c/p3p.xml). The following code doesn't work as you expect:

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

You're allowed to set P3P tags using p3p_tags().


CGI, Plack::Util


There are no known bugs in this module. Please report problems to ANAZAWA ( Patches are welcome.


Ryo Anazawa (


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

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