HTTP::Headers - Class encapsulating HTTP Message headers
require HTTP::Headers; $h = HTTP::Headers->new;
$h->header('Content-Type' => 'text/plain'); # set $ct = $h->header('Content-Type'); # get $h->remove_header('Content-Type'); # delete
Instances of this class are usually created as member variables of the "HTTP::Request" and "HTTP::Response" classes, internal to the library.
The following methods are available:
$h = HTTP::Headers->new( Date => 'Thu, 03 Feb 1994 00:00:00 GMT', Content_Type => 'text/html; version=3.2', Content_Base => 'http://www.perl.org/');
The constructor arguments are passed to the "header" method which is described below.
The header() method accepts multiple ($field => $value) pairs, which means that you can update several fields with a single invocation.
The $value argument may be a plain string or a reference to an array of strings for a multi-valued field. If the $value is provided as "undef" then the field is removed. If the $value is not given, then that header field will remain unchanged.
The old value (or values) of the last of the header fields is returned. If no such field exists "undef" will be returned.
A multi-valued field will be returned as separate values in list context and will be concatenated with ``, '' as separator in scalar context. The HTTP spec (RFC 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 ``,'' is used as part of the syntax of a single field value.
Examples:
$header->header(MIME_Version => '1.0', User_Agent => 'My-Web-Client/0.01'); $header->header(Accept => "text/html, text/plain, image/*"); $header->header(Accept => [qw(text/html text/plain image/*)]); @accepts = $header->header('Accept'); # get multiple values $accepts = $header->header('Accept'); # get values as a single string
As for the header() method, the field name ($field) is not case sensitive and '_' can be used as a replacement for '-'.
The $value argument may be a scalar or a reference to a list of scalars.
$header->push_header(Accept => 'image/jpeg'); $header->push_header(Accept => [map "image/$_", qw(gif png tiff)]);
The header field name ($field) is not case sensitive and '_' can be used as a replacement for '-'.
The $value argument may be a scalar or a reference to a list of scalars.
The header field names ($field) are not case sensitive and '_' can be used as a replacement for '-'.
The return value is the values of the fields removed. In scalar context the number of fields removed is returned.
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.
The return value is a new "HTTP::Headers" object that contains the removed headers only.
In scalar context return the number of distinct field names.
Any return values of the callback routine are ignored. The loop can be broken by raising an exception ("die"), but the caller of scan() would have to trap the exception itself.
The optional $eol parameter specifies the line ending sequence to use. The default is ``\n''. Embedded ``\n'' characters in header field values will be substituted with this line ending sequence.
Methods that deal with dates/times always convert their value to system time (seconds since Jan 1, 1970) and they also expect this kind of value when the header value is set.
$h->date(time); # set current date
# check if document is more than 1 hour old if (my $last_mod = $h->last_modified) { if ($last_mod < time - 60*60) { ... } }
$h->content_type('text/html');
The value returned will be converted to lower case, and potential parameters will be chopped off and returned as a separate value if in an array context. If there is no such header field, then the empty string is returned. This makes it safe to do the following:
if ($h->content_type eq 'text/html') { # we enter this place even if the real header value happens to # be 'TEXT/HTML; version=3.0' ... }
$h->user_agent('Mozilla/1.2');
$h->from('King Kong <king@kong.com>');
This header is no longer part of the HTTP standard.
The ``Free On-line Dictionary of Computing'' as this to say about the word referer:
<World-Wide Web> A misspelling of "referrer" which somehow made it into the {HTTP} standard. A given {web page}'s referer (sic) is the {URL} of whatever web page contains the link that the user followed to the current page. Most browsers pass this information as part of a request.
(1998-10-19)
By popular demand "referrer" exists as an alias for this method so you can avoid this misspelling in your programs and still send the right thing on the wire.
When setting the referrer, this method removes the fragment from the given URI if it is present, as mandated by RFC2616. Note that the removal does not happen automatically if using the header(), push_header() or init_header() methods to set the referrer.
When used to set the header value, it expects two arguments. E.g.:
$h->authorization_basic($uname, $password);
The method will croak if the $uname contains a colon ':'.
$h->header(":foo_bar" => 1);
These field names are returned with the ':' intact for $h->header_field_names and the $h->scan callback, but the colons do not show in $h->as_string.
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
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