1HTTP::Headers(3) User Contributed Perl Documentation HTTP::Headers(3)
2
6 HTTP::Headers - Class encapsulating HTTP Message headers
7
9 require HTTP::Headers;
10 $h = HTTP::Headers->new;
11 $h->header('Content-Type' => 'text/plain'); # set
13 $ct = $h->header('Content-Type'); # get
14 $h->remove_header('Content-Type'); # delete
15
17 The "HTTP::Headers" class encapsulates HTTP-style message headers. The
18 headers consist of attribute-value pairs also called fields, which may
19 be repeated, and which are printed in a particular order. The field
20 names are cases insensitive.
21 Instances of this class are usually created as member variables of the
23 "HTTP::Request" and "HTTP::Response" classes, internal to the library.
24 The following methods are available:
26 $h = HTTP::Headers->new
28 Constructs a new "HTTP::Headers" object. You might pass some
29 initial attribute-value pairs as parameters to the constructor.
30 E.g.:
31 $h = HTTP::Headers->new(
33 Date => 'Thu, 03 Feb 1994 00:00:00 GMT',
34 Content_Type => 'text/html; version=3.2',
35 Content_Base => 'http://www.perl.org/');
36 The constructor arguments are passed to the "header" method which
38 is described below.
39 $h->clone
41 Returns a copy of this "HTTP::Headers" object.
42 $h->header( $field )
44 $h->header( $field => $value )
45 $h->header( $f1 => $v1, $f2 => $v2, ... )
46 Get or set the value of one or more header fields. The header
47 field name ($field) is not case sensitive. To make the life easier
48 for perl users who wants to avoid quoting before the => operator,
49 you can use '_' as a replacement for '-' in header names.
50 The header() method accepts multiple ($field => $value) pairs,
52 which means that you can update several fields with a single
53 invocation.
54 The $value argument may be a plain string or a reference to an
56 array of strings for a multi-valued field. If the $value is
57 provided as "undef" then the field is removed. If the $value is
58 not given, then that header field will remain unchanged.
59 The old value (or values) of the last of the header fields is
61 returned. If no such field exists "undef" will be returned.
62 A multi-valued field will be returned as separate values in list
64 context and will be concatenated with ", " as separator in scalar
65 context. The HTTP spec (RFC 2616) promise that joining multiple
66 values in this way will not change the semantic of a header field,
67 but in practice there are cases like old-style Netscape cookies
68 (see HTTP::Cookies) where "," is used as part of the syntax of a
69 single field value.
70 Examples:
72 $header->header(MIME_Version => '1.0',
74 User_Agent => 'My-Web-Client/0.01');
75 $header->header(Accept => "text/html, text/plain, image/*");
76 $header->header(Accept => [qw(text/html text/plain image/*)]);
77 @accepts = $header->header('Accept'); # get multiple values
78 $accepts = $header->header('Accept'); # get values as a single string
79 $h->push_header( $field => $value )
81 $h->push_header( $f1 => $v1, $f2 => $v2, ... )
82 Add a new field value for the specified header field. Previous
83 values for the same field are retained.
84 As for the header() method, the field name ($field) is not case
86 sensitive and '_' can be used as a replacement for '-'.
87 The $value argument may be a scalar or a reference to a list of
89 scalars.
90 $header->push_header(Accept => 'image/jpeg');
92 $header->push_header(Accept => [map "image/$_", qw(gif png tiff)]);
93 $h->init_header( $field => $value )
95 Set the specified header to the given value, but only if no
96 previous value for that field is set.
97 The header field name ($field) is not case sensitive and '_' can be
99 used as a replacement for '-'.
100 The $value argument may be a scalar or a reference to a list of
102 scalars.
103 $h->remove_header( $field, ... )
105 This function removes the header fields with the specified names.
106 The header field names ($field) are not case sensitive and '_' can
108 be used as a replacement for '-'.
109 The return value is the values of the fields removed. In scalar
111 context the number of fields removed is returned.
112 Note that if you pass in multiple field names then it is generally
114 not possible to tell which of the returned values belonged to which
115 field.
116 $h->remove_content_headers
118 This will remove all the header fields used to describe the content
119 of a message. All header field names prefixed with "Content-" fall
120 into this category, as well as "Allow", "Expires" and
121 "Last-Modified". RFC 2616 denotes these fields as Entity Header
122 Fields.
123 The return value is a new "HTTP::Headers" object that contains the
125 removed headers only.
126 $h->clear
128 This will remove all header fields.
129 $h->header_field_names
131 Returns the list of distinct names for the fields present in the
132 header. The field names have case as suggested by HTTP spec, and
133 the names are returned in the recommended "Good Practice" order.
134 In scalar context return the number of distinct field names.
136 $h->scan( \&process_header_field )
138 Apply a subroutine to each header field in turn. The callback
139 routine is called with two parameters; the name of the field and a
140 single value (a string). If a header field is multi-valued, then
141 the routine is called once for each value. The field name passed
142 to the callback routine has case as suggested by HTTP spec, and the
143 headers will be visited in the recommended "Good Practice" order.
144 Any return values of the callback routine are ignored. The loop
146 can be broken by raising an exception ("die"), but the caller of
147 scan() would have to trap the exception itself.
148 $h->as_string
150 $h->as_string( $eol )
151 Return the header fields as a formatted MIME header. Since it
152 internally uses the "scan" method to build the string, the result
153 will use case as suggested by HTTP spec, and it will follow
154 recommended "Good Practice" of ordering the header fields. Long
155 header values are not folded.
156 The optional $eol parameter specifies the line ending sequence to
158 use. The default is "\n". Embedded "\n" characters in header
159 field values will be substituted with this line ending sequence.
160
162 The most frequently used headers can also be accessed through the
163 following convenience methods. Most of these methods can both be used
164 to read and to set the value of a header. The header value is set if
165 you pass an argument to the method. The old header value is always
166 returned. If the given header did not exist then "undef" is returned.
167 Methods that deal with dates/times always convert their value to system
169 time (seconds since Jan 1, 1970) and they also expect this kind of
170 value when the header value is set.
171 $h->date
173 This header represents the date and time at which the message was
174 originated. E.g.:
175 $h->date(time); # set current date
177 $h->expires
179 This header gives the date and time after which the entity should
180 be considered stale.
181 $h->if_modified_since
183 $h->if_unmodified_since
184 These header fields are used to make a request conditional. If the
185 requested resource has (or has not) been modified since the time
186 specified in this field, then the server will return a "304 Not
187 Modified" response instead of the document itself.
188 $h->last_modified
190 This header indicates the date and time at which the resource was
191 last modified. E.g.:
192 # check if document is more than 1 hour old
194 if (my $last_mod = $h->last_modified) {
195 if ($last_mod < time - 60*60) {
196 ...
197 }
198 }
199 $h->content_type
201 The Content-Type header field indicates the media type of the
202 message content. E.g.:
203 $h->content_type('text/html');
205 The value returned will be converted to lower case, and potential
207 parameters will be chopped off and returned as a separate value if
208 in an array context. If there is no such header field, then the
209 empty string is returned. This makes it safe to do the following:
210 if ($h->content_type eq 'text/html') {
212 # we enter this place even if the real header value happens to
213 # be 'TEXT/HTML; version=3.0'
214 ...
215 }
216 $h->content_type_charset
218 Returns the upper-cased charset specified in the Content-Type
219 header. In list context return the lower-cased bare content type
220 followed by the upper-cased charset. Both values will be "undef"
221 if not specified in the header.
222 $h->content_is_text
224 Returns TRUE if the Content-Type header field indicate that the
225 content is textual.
226 $h->content_is_html
228 Returns TRUE if the Content-Type header field indicate that the
229 content is some kind of HTML (including XHTML). This method can't
230 be used to set Content-Type.
231 $h->content_is_xhtml
233 Returns TRUE if the Content-Type header field indicate that the
234 content is XHTML. This method can't be used to set Content-Type.
235 $h->content_is_xml
237 Returns TRUE if the Content-Type header field indicate that the
238 content is XML. This method can't be used to set Content-Type.
239 $h->content_encoding
241 The Content-Encoding header field is used as a modifier to the
242 media type. When present, its value indicates what additional
243 encoding mechanism has been applied to the resource.
244 $h->content_length
246 A decimal number indicating the size in bytes of the message
247 content.
248 $h->content_language
250 The natural language(s) of the intended audience for the message
251 content. The value is one or more language tags as defined by RFC
252 1766. Eg. "no" for some kind of Norwegian and "en-US" for English
253 the way it is written in the US.
254 $h->title
256 The title of the document. In libwww-perl this header will be
257 initialized automatically from the <TITLE>...</TITLE> element of
258 HTML documents. This header is no longer part of the HTTP
259 standard.
260 $h->user_agent
262 This header field is used in request messages and contains
263 information about the user agent originating the request. E.g.:
264 $h->user_agent('Mozilla/5.0 (compatible; MSIE 7.0; Windows NT 6.0)');
266 $h->server
268 The server header field contains information about the software
269 being used by the originating server program handling the request.
270 $h->from
272 This header should contain an Internet e-mail address for the human
273 user who controls the requesting user agent. The address should be
274 machine-usable, as defined by RFC822. E.g.:
275 $h->from('King Kong <king@kong.com>');
277 This header is no longer part of the HTTP standard.
279 $h->referer
281 Used to specify the address (URI) of the document from which the
282 requested resource address was obtained.
283 The "Free On-line Dictionary of Computing" as this to say about the
285 word referer:
286 <World-Wide Web> A misspelling of "referrer" which
288 somehow made it into the {HTTP} standard. A given {web
289 page}'s referer (sic) is the {URL} of whatever web page
290 contains the link that the user followed to the current
291 page. Most browsers pass this information as part of a
292 request.
293 (1998-10-19)
295 By popular demand "referrer" exists as an alias for this method so
297 you can avoid this misspelling in your programs and still send the
298 right thing on the wire.
299 When setting the referrer, this method removes the fragment from
301 the given URI if it is present, as mandated by RFC2616. Note that
302 the removal does not happen automatically if using the header(),
303 push_header() or init_header() methods to set the referrer.
304 $h->www_authenticate
306 This header must be included as part of a "401 Unauthorized"
307 response. The field value consist of a challenge that indicates
308 the authentication scheme and parameters applicable to the
309 requested URI.
310 $h->proxy_authenticate
312 This header must be included in a "407 Proxy Authentication
313 Required" response.
314 $h->authorization
316 $h->proxy_authorization
317 A user agent that wishes to authenticate itself with a server or a
318 proxy, may do so by including these headers.
319 $h->authorization_basic
321 This method is used to get or set an authorization header that use
322 the "Basic Authentication Scheme". In array context it will return
323 two values; the user name and the password. In scalar context it
324 will return "uname:password" as a single string value.
325 When used to set the header value, it expects two arguments. E.g.:
327 $h->authorization_basic($uname, $password);
329 The method will croak if the $uname contains a colon ':'.
331 $h->proxy_authorization_basic
333 Same as authorization_basic() but will set the "Proxy-
334 Authorization" header instead.
335
337 The header field name spelling is normally canonicalized including the
338 '_' to '-' translation. There are some application where this is not
339 appropriate. Prefixing field names with ':' allow you to force a
340 specific spelling. For example if you really want a header field name
341 to show up as "foo_bar" instead of "Foo-Bar", you might set it like
342 this:
343 $h->header(":foo_bar" => 1);
345 These field names are returned with the ':' intact for
347 $h->header_field_names and the $h->scan callback, but the colons do not
348 show in $h->as_string.
349
351 Copyright 1995-2005 Gisle Aas.
352 This library is free software; you can redistribute it and/or modify it
354 under the same terms as Perl itself.
355perl v5.16.3 2012-10-20 HTTP::Headers(3)