http::headers.3

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.\" ========================================================================
.\"
.IX Title "HTTP::Headers 3"
.TH HTTP::Headers 3 "2005-12-08" "perl v5.10.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
HTTP::Headers \- Class encapsulating HTTP Message headers
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\& require HTTP::Headers;
\& $h = HTTP::Headers\->new;
\&
\& $h\->header(\*(AqContent\-Type\*(Aq => \*(Aqtext/plain\*(Aq);  # set
\& $ct = $h\->header(\*(AqContent\-Type\*(Aq);            # get
\& $h\->remove_header(\*(AqContent\-Type\*(Aq);           # delete
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \f(CW\*(C`HTTP::Headers\*(C'\fR class encapsulates HTTP-style message headers.
The headers consist of attribute-value pairs also called fields, which
may be repeated, and which are printed in a particular order.  The
field names are cases insensitive.
.PP
Instances of this class are usually created as member variables of the
\&\f(CW\*(C`HTTP::Request\*(C'\fR and \f(CW\*(C`HTTP::Response\*(C'\fR classes, internal to the
library.
.PP
The following methods are available:
.ie n .IP "$h = HTTP::Headers\->new" 4
.el .IP "\f(CW$h\fR = HTTP::Headers\->new" 4
.IX Item "$h = HTTP::Headers->new"
Constructs a new \f(CW\*(C`HTTP::Headers\*(C'\fR object.  You might pass some initial
attribute-value pairs as parameters to the constructor.  \fIE.g.\fR:
.Sp
.Vb 4
\& $h = HTTP::Headers\->new(
\&       Date         => \*(AqThu, 03 Feb 1994 00:00:00 GMT\*(Aq,
\&       Content_Type => \*(Aqtext/html; version=3.2\*(Aq,
\&       Content_Base => \*(Aqhttp://www.perl.org/\*(Aq);
.Ve
.Sp
The constructor arguments are passed to the \f(CW\*(C`header\*(C'\fR method which is
described below.
.ie n .IP "$h\->clone" 4
.el .IP "\f(CW$h\fR\->clone" 4
.IX Item "$h->clone"
Returns a copy of this \f(CW\*(C`HTTP::Headers\*(C'\fR object.
.ie n .IP "$h\fR\->header( \f(CW$field )" 4
.el .IP "\f(CW$h\fR\->header( \f(CW$field\fR )" 4
.IX Item "$h->header( $field )"
.PD 0
.ie n .IP "$h\fR\->header( \f(CW$field\fR => \f(CW$value, ... )" 4
.el .IP "\f(CW$h\fR\->header( \f(CW$field\fR => \f(CW$value\fR, ... )" 4
.IX Item "$h->header( $field => $value, ... )"
.PD
Get or set the value of one or more header fields.  The header field
name ($field) is not case sensitive.  To make the life easier for perl
users who wants to avoid quoting before the => operator, you can use
\&'_' as a replacement for '\-' in header names.
.Sp
The \fIheader()\fR method accepts multiple ($field => \f(CW$value\fR) pairs, which
means that you can update several fields with a single invocation.
.Sp
The \f(CW$value\fR argument may be a plain string or a reference to an array
of strings for a multi-valued field. If the \f(CW$value\fR is provided as
\&\f(CW\*(C`undef\*(C'\fR then the field is removed.  If the \f(CW$value\fR is not given, then
that header field will remain unchanged.
.Sp
The old value (or values) of the last of the header fields is returned.
If no such field exists \f(CW\*(C`undef\*(C'\fR will be returned.
.Sp
A multi-valued field will be returned as separate values in list
context and will be concatenated with \*(L", \*(R" as separator in scalar
context.  The \s-1HTTP\s0 spec (\s-1RFC\s0 2616) promise that joining multiple
values in this way will not change the semantic of a header field, but
in practice there are cases like old-style Netscape cookies (see
HTTP::Cookies) where \*(L",\*(R" is used as part of the syntax of a single
field value.
.Sp
Examples:
.Sp
.Vb 6
\& $header\->header(MIME_Version => \*(Aq1.0\*(Aq,
\&                 User_Agent   => \*(AqMy\-Web\-Client/0.01\*(Aq);
\& $header\->header(Accept => "text/html, text/plain, image/*");
\& $header\->header(Accept => [qw(text/html text/plain image/*)]);
\& @accepts = $header\->header(\*(AqAccept\*(Aq);  # get multiple values
\& $accepts = $header\->header(\*(AqAccept\*(Aq);  # get values as a single string
.Ve
.ie n .IP "$h\fR\->push_header( \f(CW$field\fR => \f(CW$value )" 4
.el .IP "\f(CW$h\fR\->push_header( \f(CW$field\fR => \f(CW$value\fR )" 4
.IX Item "$h->push_header( $field => $value )"
Add a new field value for the specified header field.  Previous values
for the same field are retained.
.Sp
As for the \fIheader()\fR method, the field name ($field) is not case
sensitive and '_' can be used as a replacement for '\-'.
.Sp
The \f(CW$value\fR argument may be a scalar or a reference to a list of
scalars.
.Sp
.Vb 2
\& $header\->push_header(Accept => \*(Aqimage/jpeg\*(Aq);
\& $header\->push_header(Accept => [map "image/$_", qw(gif png tiff)]);
.Ve
.ie n .IP "$h\fR\->init_header( \f(CW$field\fR => \f(CW$value )" 4
.el .IP "\f(CW$h\fR\->init_header( \f(CW$field\fR => \f(CW$value\fR )" 4
.IX Item "$h->init_header( $field => $value )"
Set the specified header to the given value, but only if no previous
value for that field is set.
.Sp
The header field name ($field) is not case sensitive and '_'
can be used as a replacement for '\-'.
.Sp
The \f(CW$value\fR argument may be a scalar or a reference to a list of
scalars.
.ie n .IP "$h\fR\->remove_header( \f(CW$field, ... )" 4
.el .IP "\f(CW$h\fR\->remove_header( \f(CW$field\fR, ... )" 4
.IX Item "$h->remove_header( $field, ... )"
This function removes the header fields with the specified names.
.Sp
The header field names ($field) are not case sensitive and '_'
can be used as a replacement for '\-'.
.Sp
The return value is the values of the fields removed.  In scalar
context the number of fields removed is returned.
.Sp
Note that if you pass in multiple field names then it is generally not
possible to tell which of the returned values belonged to which field.
.ie n .IP "$h\->remove_content_headers" 4
.el .IP "\f(CW$h\fR\->remove_content_headers" 4