From f1883aab788194cf1154ca1b5258a6307e3f5149 Mon Sep 17 00:00:00 2001 From: jim winstead Date: Wed, 31 Oct 2001 22:27:31 +0000 Subject: [PATCH] cleaned up header(), incorporated all notes. git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@61274 c90b9560-bf6c-de11-be94-00142212c4b1 --- functions/http.xml | 155 ++++++++++++++++++++++++++++++++------------- 1 file changed, 110 insertions(+), 45 deletions(-) diff --git a/functions/http.xml b/functions/http.xml index ec57f0eb52..e89843644d 100644 --- a/functions/http.xml +++ b/functions/http.xml @@ -1,5 +1,5 @@ - + HTTP functions HTTP @@ -26,34 +26,32 @@ - The header function is used at the top of an - HTML file to send raw HTTP - header strings. See the HTTP 1.1 - Specification for more information on raw http headers. + header is used to send raw + HTTP headers. See the HTTP/1.1 specification for more + information on HTTP headers. - The optional replace 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 replace 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: -header('www-authenticate: Negociate'); -header('www-authenticate: NTLM',false); +header('WWW-Authenticate: Negotiate'); +header('WWW-Authenticate: NTLM',false); There are two special-case header calls. The first is the - "Location" 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. + "Location" header. Not only does it send this header back + to the browser, but it also returns a REDIRECT + (302) status code to the browser. -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 - HTTP 1.1 requires an absolute URI as argument to + HTTP/1.1 requires an absolute URI as argument to Location: - 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 dirname - 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'], $HTTP_SERVER_VARS['PHP_SELF'] + and dirname to make an absolute URI from a + relative one yourself: -header ("Location: http://".$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); - The second special-case is any header that starts with the - string, "HTTP/" (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, "HTTP/" (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 ErrorDocument directive), you may want to + make sure that your script generates the proper status code. -header ("HTTP/1.0 404 Not Found"); +header("HTTP/1.0 404 Not Found"); + + + In PHP 3, this only works when PHP is compiled as an Apache + module. You can achieve the same effect using the + Status header. + + +header("Status: 404 Not Found"); + + + + - 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 -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 + + + 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. + + + Additionally, session_cache_limiter and + the session.cache_limiter configuration + setting can be used to automatically generate the correct + caching-related headers when sessions are being used. + + - Remember that the header function must be + Remember that header 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 include, or require, 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 header is called. The same problem exists when using a single PHP/HTML file. -<?php require("user_logging.inc") ?> +<?php require("user_logging.inc") ?> -<?php header ("Content-Type: audio/x-pn-realaudio"); ?> +<?php header ("Content-type: audio/x-pn-realaudio"); ?> // Broken, Note the blank lines above + + + 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 + ob_start and ob_end_flush + in your script, or setting the output_buffering + configuration directive on in your php.ini or + server configuration files. + + - See also headers_sent + 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 Content-Disposition header to + supply a recommended filename and force the browser to display the + save dialog. + + +<?php +header("Content-type: application/pdf"); +header("Content-Disposition: attachment; filename=downloaded.pdf"); + +/* ... output pdf file ... */ + + + + + 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. + + + + + See also headers_sent, + setcookie, and the section on + HTTP authentication.