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RE: Combining multiple message-header fields

From: Joris Dobbelsteen <joris.dobbelsteen@mail.com>
Date: Sat, 15 Jul 2000 20:14:49 +0200
To: "WWW WG (E-mail)" <www-talk@w3.org>
Message-ID: <000f01bfee88$90a2bb10$0d0aa8c0@THUIS.LOCAL>
It doesn't matter: You can send

Accept: text/html
Accept: image/*
- or -
Accept: text/html, image/*

If you use a proxy it can be send like this:

 | Accept: text/html
 | Accept: image/*
 | Accept: text/html, image/*

What may not hapen is that you make:
Accept: image/*, text/html
The order of the items is changed....

What is most recommended is to combine them in one header, because it saves
(very little, but some) network bandwidth...

 - Joris Dobbelsteen

-----Original Message-----
From: Bjoern Hoehrmann [mailto:derhoermi@gmx.net]
Sent: zaterdag 15 juli 2000 17:45
To: http-wg@cuckoo.hpl.hp.com
Subject: Combining multiple message-header fields


RFC2616 says:

| 4.2 Message Headers
| [...]
|    Multiple message-header fields with the same field-name MAY be
|    present in a message if and only if the entire field-value for that
|    header field is defined as a comma-separated list [i.e., #(values)].
|    It MUST be possible to combine the multiple header fields into one
|    "field-name: field-value" pair, without changing the semantics of the
|    message, by appending each subsequent field-value to the first, each
|    separated by a comma. The order in which header fields with the same
|    field-name are received is therefore significant to the
|    interpretation of the combined field value, and thus a proxy MUST NOT
|    change the order of these field values when a message is forwarded.

I'm building a HTTP UserAgent with PHP and now i'm dealing with this
message-header fields. If my UserAgent receives such multiple fields, should
it combine these fields into one or should it keep the multiple fields and
send it to the server (if present in a request)? The problem behind this is
the storage of this header fields. Currently i have an associative array
does something like

Accept => array(text/html, image/*)

if there was

Accept: text/html
Accept: image/*

but when someone wants the value of Accept i only want to return a string
therefor i only return the first value i.e. text/html which does not meet
someones expactation.

I appreciate your help,
  Björn Höhrmann
"Jede  Straße,  der  man konsequent \ und du wirst ihn in Gänze sehen.
bis zu ihrem Ende folgt,  führt un- ) Stehst Du auf seinem Gipfel wird
weigerlich  ins  Nichts.   Erklimme ( er  für  Dich  unsichtbar" -- P.
einen  Berg nur ein kleines  Stück, \ Irulan <http://bjoernsworld.de/>
Received on Saturday, 15 July 2000 14:13:31 UTC

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