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cleaned up header(), incorporated all notes.

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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@61274 c90b9560-bf6c-de11-be94-00142212c4b1
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jim winstead 2001-10-31 22:27:31 +00:00
parent b73e38061b
commit f1883aab78
1 changed files with 110 additions and 45 deletions
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155
functions/http.xml
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@ -1,5 +1,5 @@
<?xml encoding="iso-8859-1"?>
<!-- $Revision: 1.29 $ -->
<!-- $Revision: 1.30 $ -->
<reference id="ref.http">
<title>HTTP functions</title>
<titleabbrev>HTTP</titleabbrev>
@ -26,34 +26,32 @@
</funcprototype>
</funcsynopsis>
<para>
The <function>header</function> function is used at the top of an
<acronym>HTML</acronym> file to send raw <acronym>HTTP</acronym>
header strings. See the <ulink url="&spec.http1.1;">HTTP 1.1
Specification</ulink> for more information on raw http headers.
<function>header</function> is used to send raw
<acronym>HTTP</acronym> headers. See the <ulink
url="&spec.http1.1;">HTTP/1.1 specification</ulink> for more
information on <acronym>HTTP</acronym> headers.
</para>
<para>
The optional <parameter>replace</parameter> parameter indicates whether
the header should replace a previous similar header, or add a second header
of the same type. By default it will replace, but if you pass in &false; as
the second argument you can force multiple headers of the same type. For
example:
The optional <parameter>replace</parameter> parameter indicates
whether the header should replace a previous similar header, or
add a second header of the same type. By default it will replace,
but if you pass in &false; as the second argument you can force
multiple headers of the same type. For example:
<informalexample>
<programlisting role="php">
header('www-authenticate: Negociate');
header('www-authenticate: NTLM',false);
header('WWW-Authenticate: Negotiate');
header('WWW-Authenticate: NTLM',false);
</programlisting>
</informalexample>
</para>
<para>
There are two special-case header calls. The first is the
&quot;Location&quot; header. Not only does it send this header
back to the browser, it also returns a REDIRECT status code to
Apache. From a script writer's point of view this should not be
important, but for people who understand Apache internals it is
important to understand.
&quot;Location&quot; header. Not only does it send this header back
to the browser, but it also returns a <literal>REDIRECT</literal>
(302) status code to the browser.
<informalexample>
<programlisting role="php">
header ("Location: http://www.php.net/"); /* Redirect browser
header("Location: http://www.php.net/"); /* Redirect browser
to PHP web site */
exit; /* Make sure that code below does
not get executed when we redirect. */
@ -62,71 +60,138 @@ exit; /* Make sure that code below does
</para>
<note>
<para>
HTTP 1.1 requires an absolute URI as argument to
HTTP/1.1 requires an absolute <acronym>URI</acronym> as argument to
<ulink url="&spec.http1.1;-sec14.html#sec14.30">Location:</ulink>
including protocol, hostname and absolute path. Some clients
might accept relative URIs but you definetly should not rely on
it. You can usually use $HTTP_SERVER_VARS['HTTP_HOST'],
$HTTP_SERVER_VARS['PHP_SELF'] and <function>dirname</function>
to make an absolute URI from a relative one yourself:
including the scheme, hostname and absolute path, but
some clients accept relative URIs. You can usually use
$HTTP_SERVER_VARS['HTTP_HOST'], $HTTP_SERVER_VARS['PHP_SELF']
and <function>dirname</function> to make an absolute URI from a
relative one yourself:
<informalexample>
<programlisting>
header ("Location: http://".$HTTP_SERVER_VARS['HTTP_HOST']
."/".dirname($HTTP_SERVER_VARS['PHP_SELF'])
."/".$relative_url);
header("Location: http://".$HTTP_SERVER_VARS['HTTP_HOST']
."/".dirname($HTTP_SERVER_VARS['PHP_SELF'])
."/".$relative_url);
</programlisting>
</informalexample>
</para>
</note>
<para>
The second special-case is any header that starts with the
string, &quot;HTTP/&quot; (case is not significant). For
example, if you have your ErrorDocument 404 Apache directive
pointed to a PHP script, it would be a good idea to make sure
that your PHP script is actually generating a 404. The first
thing you do in your script should then be:
The second special case is any header that starts with the
string, &quot;<literal>HTTP/</literal>&quot; (case is not
significant), which will be used to figure out the HTTP status
code to send. For example, if you have configured Apache to
use a PHP script to handle requests for missing files (using
the <literal>ErrorDocument</literal> directive), you may want to
make sure that your script generates the proper status code.
<informalexample>
<programlisting role="php">
header ("HTTP/1.0 404 Not Found");
header("HTTP/1.0 404 Not Found");
</programlisting>
</informalexample>
<note>
<para>
In PHP 3, this only works when PHP is compiled as an Apache
module. You can achieve the same effect using the
<literal>Status</literal> header.
<informalexample>
<programlisting role="php">
header("Status: 404 Not Found");
</programlisting>
</informalexample>
</para>
</note>
</para>
<para>
PHP scripts often generate dynamic HTML that must not be cached
PHP scripts often generate dynamic content that must not be cached
by the client browser or any proxy caches between the server and the
client browser. Many proxies and clients can be forced to disable
caching with
<informalexample>
<programlisting role="php">
header ("Expires: Mon, 26 Jul 1997 05:00:00 GMT"); // Date in the past
header ("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
// always modified
header ("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1
header ("Pragma: no-cache"); // HTTP/1.0
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT"); // Date in the past
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
// always modified
header("Cache-Control: no-store, no-cache, must-revalidate"); // HTTP/1.1
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache"); // HTTP/1.0
</programlisting>
</informalexample>
<note>
<para>
You may find that your pages aren't cached even if you don't
output all of the headers above. There are a number of options
that users may be able to set for their browser that change its
default caching behavior. By sending the headers above, you should
override any settings that may otherwise cause the output of your
script to be cached.
</para>
<para>
Additionally, <function>session_cache_limiter</function> and
the <literal>session.cache_limiter</literal> configuration
setting can be used to automatically generate the correct
caching-related headers when sessions are being used.
</para>
</note>
</para>
<para>
Remember that the <function>header</function> function must be
Remember that <function>header</function> must be
called before any actual output is sent, either by normal HTML
tags blank lines in a file, or from PHP. It is a very common
error to read code with <function>include</function>, or
<function>require</function>, functions, or another file access
function, and have spaces or empty lines that will output before
function, and have spaces or empty lines that are output before
<function>header</function> is called. The same problem exists
when using a single PHP/HTML file.
<informalexample>
<programlisting role="php">
&lt;?php require("user_logging.inc") ?>
&lt;?php require("user_logging.inc") ?&gt;
&lt;?php header ("Content-Type: audio/x-pn-realaudio"); ?>
&lt;?php header ("Content-type: audio/x-pn-realaudio"); ?&gt;
// Broken, Note the blank lines above
</programlisting>
</informalexample>
<note>
<para>
In PHP 4, you can use output buffering to get around this problem,
with the overhead of all of your output to the browser being buffered
in the server until you send it. You can do this by calling
<function>ob_start</function> and <function>ob_end_flush</function>
in your script, or setting the <literal>output_buffering</literal>
configuration directive on in your <filename>php.ini</filename> or
server configuration files.
</para>
</note>
</para>
<para>
See also <function>headers_sent</function>
If you want the user to be prompted to save the data you are
sending, such as a generated PDF file, you can use the <ulink
url="&url.rfc1806;">Content-Disposition</ulink> header to
supply a recommended filename and force the browser to display the
save dialog.
<informalexample>
<programlisting role="php">
&lt;?php
header("Content-type: application/pdf");
header("Content-Disposition: attachment; filename=downloaded.pdf");
/* ... output pdf file ... */
</programlisting>
</informalexample>
<note>
<para>
There is a bug in Microsoft Internet Explorer 4.01 that prevents
this from working. There is no workaround. There is also a bug
in Microsoft Internet Explorer 5.5 that interferes with this,
which can be resolved by upgrading to Service Pack 2 or later.
</para>
</note>
</para>
<para>
See also <function>headers_sent</function>,
<function>setcookie</function>, and the section on
<link linkend="features.http-auth">HTTP authentication</link>.
</para>
</refsect1>
</refentry>