PHP 5.6.0RC3 is available

header

(PHP 4, PHP 5)

headerSend a raw HTTP header

Descrizione

void header ( string $string [, bool $replace = true [, int $http_response_code ]] )

header() is used to send a raw HTTP header. See the » HTTP/1.1 specification for more information on HTTP headers.

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 are output before header() is called. The same problem exists when using a single PHP/HTML file.

<html>
<?php
/* This will give an error. Note the output
 * above, which is before the header() call */
header('Location: http://www.example.com/');
exit;
?>

Elenco dei parametri

string

The header string.

There are two special-case header calls. The first is a 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.

<?php
header
("HTTP/1.0 404 Not Found");
?>

The second special case is the "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 unless the 201 or a 3xx status code has already been set.

<?php
header
("Location: http://www.example.com/"); /* Redirect browser */

/* Make sure that code below does not get executed when we redirect. */
exit;
?>

replace

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:

<?php
header
('WWW-Authenticate: Negotiate');
header('WWW-Authenticate: NTLM'false);
?>

http_response_code

Forces the HTTP response code to the specified value. Note that this parameter only has an effect if the string is not empty.

Valori restituiti

Nessun valore viene restituito.

Log delle modifiche

Versione Descrizione
4.4.2 and 5.1.2 This function now prevents more than one header to be sent at once as a protection against header injection attacks.
4.3.0 The http_response_code parameter was added.
4.0.4 The replace parameter was added.

Esempi

Example #1 Download dialog

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
// We'll be outputting a PDF
header('Content-type: application/pdf');

// It will be called downloaded.pdf
header('Content-Disposition: attachment; filename="downloaded.pdf"');

// The PDF source is in original.pdf
readfile('original.pdf');
?>

Example #2 Caching directives

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:

<?php
header
("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1
header("Expires: Sat, 26 Jul 1997 05:00:00 GMT"); // Date in the past
?>

Nota:

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.

Note

Nota:

Gli header sono accessibili (e emessi nell'output) quando è in uso un SAPI che li supporta.

Nota:

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.

Nota:

The HTTP status header line will always be the first sent to the client, regardless of the actual header() call being the first or not. The status may be overridden by calling header() with a new status line at any time unless the HTTP headers have already been sent.

Nota:

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.

Nota: If safe mode is enabled the uid of the script is added to the realm part of the WWW-Authenticate header if you set this header (used for HTTP Authentication).

Nota:

HTTP/1.1 requires an absolute URI as argument to » Location: including the scheme, hostname and absolute path, but some clients accept relative URIs. You can usually use $_SERVER['HTTP_HOST'], $_SERVER['PHP_SELF'] and dirname() to make an absolute URI from a relative one yourself:

<?php
/* Redirect to a different page in the current directory that was requested */
$host  $_SERVER['HTTP_HOST'];
$uri   rtrim(dirname($_SERVER['PHP_SELF']), '/\\');
$extra 'mypage.php';
header("Location: http://$host$uri/$extra");
exit;
?>

Nota:

Session ID is not passed with Location header even if session.use_trans_sid is enabled. It must by passed manually using SID constant.

Vedere anche:

add a note add a note

User Contributed Notes 23 notes

up
36
mjt at jpeto dot net
5 years ago
I strongly recommend, that you use

header($_SERVER["SERVER_PROTOCOL"]." 404 Not Found");

instead of

header("HTTP/1.1 404 Not Found");

I had big troubles with an Apache/2.0.59 (Unix) answering in HTTP/1.0 while I (accidentially) added a "HTTP/1.1 200 Ok" - Header.

Most of the pages were displayed correct, but on some of them apache added weird content to it:

A 4-digits HexCode on top of the page (before any output of my php script), seems to be some kind of checksum, because it changes from page to page and browser to browser. (same code for same page and browser)

"0" at the bottom of the page (after the complete output of my php script)

It took me quite a while to find out about the wrong protocol in the HTTP-header.
up
6
bebertjean at yahoo dot fr
5 years ago
If using the 'header' function for the downloading of files, especially if you're passing the filename as a variable, remember to surround the filename with double quotes, otherwise you'll have problems in Firefox as soon as there's a space in the filename.

So instead of typing:

<?php
  header
("Content-Disposition: attachment; filename=" . basename($filename));
?>

you should type:

<?php
  header
("Content-Disposition: attachment; filename=\"" . basename($filename) . "\"");
?>

If you don't do this then when the user clicks on the link for a file named "Example file with spaces.txt", then Firefox's Save As dialog box will give it the name "Example", and it will have no extension.

See the page called "Filenames_with_spaces_are_truncated_upon_download" at
http://kb.mozillazine.org/ for more information. (Sorry, the site won't let me post such a long link...)
up
16
Dylan at WeDefy dot com
6 years ago
A quick way to make redirects permanent or temporary is to make use of the $http_response_code parameter in header().

<?php
// 301 Moved Permanently
header("Location: /foo.php",TRUE,301);

// 302 Found
header("Location: /foo.php",TRUE,302);
header("Location: /foo.php");

// 303 See Other
header("Location: /foo.php",TRUE,303);

// 307 Temporary Redirect
header("Location: /foo.php",TRUE,307);
?>

The HTTP status code changes the way browsers and robots handle redirects, so if you are using header(Location:) it's a good idea to set the status code at the same time.  Browsers typically re-request a 307 page every time, cache a 302 page for the session, and cache a 301 page for longer, or even indefinitely.  Search engines typically transfer "page rank" to the new location for 301 redirects, but not for 302, 303 or 307. If the status code is not specified, header('Location:') defaults to 302.
up
11
mandor at mandor dot net
8 years ago
When using PHP to output an image, it won't be cached by the client so if you don't want them to download the image each time they reload the page, you will need to emulate part of the HTTP protocol.

Here's how:

<?php

   
// Test image.
   
$fn = '/test/foo.png';

   
// Getting headers sent by the client.
   
$headers = apache_request_headers();

   
// Checking if the client is validating his cache and if it is current.
   
if (isset($headers['If-Modified-Since']) && (strtotime($headers['If-Modified-Since']) == filemtime($fn))) {
       
// Client's cache IS current, so we just respond '304 Not Modified'.
       
header('Last-Modified: '.gmdate('D, d M Y H:i:s', filemtime($fn)).' GMT', true, 304);
    } else {
       
// Image not cached or cache outdated, we respond '200 OK' and output the image.
       
header('Last-Modified: '.gmdate('D, d M Y H:i:s', filemtime($fn)).' GMT', true, 200);
       
header('Content-Length: '.filesize($fn));
       
header('Content-Type: image/png');
        print
file_get_contents($fn);
    }

?>

That way foo.png will be properly cached by the client and you'll save bandwith. :)
up
6
ben at indietorrent dot org
2 years ago
Be aware that sending binary files to the user-agent (browser) over an encrypted connection (SSL/TLS) will fail in IE (Internet Explorer) versions 5, 6, 7, and 8 if any of the following headers is included:

Cache-control:no-store
Cache-control:no-cache

See: http://support.microsoft.com/kb/323308

Workaround: do not send those headers.

Also, be aware that IE versions 5, 6, 7, and 8 double-compress already-compressed files and do not reverse the process correctly, so ZIP files and similar are corrupted on download.

Workaround: disable compression (beyond text/html) for these particular versions of IE, e.g., using Apache's "BrowserMatch" directive. The following example disables compression in all versions of IE:

BrowserMatch ".*MSIE.*" gzip-only-text/html
up
6
Marcel G
4 years ago
Several times this one is asked on the net but an answer could not be found in the docs on php.net ...

If you want to redirect an user and tell him he will be redirected, e. g. "You will be redirected in about 5 secs. If not, click here." you cannot use header( 'Location: ...' ) as you can't sent any output before the headers are sent.

So, either you have to use the HTML meta refresh thingy or you use the following:

<?php
  header
( "refresh:5;url=wherever.php" );
  echo
'You\'ll be redirected in about 5 secs. If not, click <a href="wherever.php">here</a>.';
?>

Hth someone
up
8
bMindful at fleetingiamge dot org
11 years ago
If you haven't used, HTTP Response 204 can be very convenient. 204 tells the server to immediately termiante this request. This is helpful if you want a javascript (or similar) client-side function to execute a server-side function without refreshing or changing the current webpage. Great for updating database, setting global variables, etc.

     header("status: 204");  (or the other call)
     header("HTTP/1.0 204 No Response");
up
5
shutout2730 at yahoo dot com
5 years ago
It is important to note that headers are actually sent when the first byte is output to the browser. If you are replacing headers in your scripts, this means that the placement of echo/print statements and output buffers may actually impact which headers are sent. In the case of redirects, if you forget to terminate your script after sending the header, adding a buffer or sending a character may change which page your users are sent to.

This redirects to 2.html since the second header replaces the first.

<?php
header
("location: 1.html");
header("location: 2.html"); //replaces 1.html
?>

This redirects to 1.html since the header is sent as soon as the echo happens. You also won't see any "headers already sent" errors because the browser follows the redirect before it can display the error.

<?php
header
("location: 1.html");
echo
"send data";
header("location: 2.html"); //1.html already sent
?>

Wrapping the previous example in an output buffer actually changes the behavior of the script! This is because headers aren't sent until the output buffer is flushed.

<?php
ob_start
();
header("location: 1.html");
echo
"send data";
header("location: 2.html"); //replaces 1.html
ob_end_flush(); //now the headers are sent
?>
up
3
scott at lucentminds dot com
4 years ago
If you want to remove a header and keep it from being sent as part of the header response, just provide nothing as the header value after the header name. For example...

PHP, by default, always returns the following header:

"Content-Type: text/html"

Which your entire header response will look like

HTTP/1.1 200 OK
Server: Apache/2.2.11 (Unix)
X-Powered-By: PHP/5.2.8
Date: Fri, 16 Oct 2009 23:05:07 GMT
Content-Type: text/html; charset=UTF-8
Connection: close

If you call the header name with no value like so...

<?php

    header
( 'Content-Type:' );

?>

Your headers now look like this:

HTTP/1.1 200 OK
Server: Apache/2.2.11 (Unix)
X-Powered-By: PHP/5.2.8
Date: Fri, 16 Oct 2009 23:05:07 GMT
Connection: close
up
1
Kal
7 years ago
I spent a long time trying to determine why Internet Explorer 7 wasn't prompting the user to save a download based on the filename specified on a "'Content-Disposition: attachment; filename=..." header line.

I eventually determined that my Apache installation was adding an additional header: "Vary: Host", which was throwing IE - as per http://support.microsoft.com/kb/824847

I found manually setting the Vary header from within PHP as follows header('Vary: User-Agent'); allowed IE to behave as intended.

Hope this saves someone else some time,

- Kal
up
5
mzheng[no-spam-thx] at ariba dot com
5 years ago
For large files (100+ MBs), I found that it is essential to flush the file content ASAP, otherwise the download dialog doesn't show until a long time or never.

<?php
header
("Content-Disposition: attachment; filename=" . urlencode($file));   
header("Content-Type: application/force-download");
header("Content-Type: application/octet-stream");
header("Content-Type: application/download");
header("Content-Description: File Transfer");            
header("Content-Length: " . filesize($file));
flush(); // this doesn't really matter.

$fp = fopen($file, "r");
while (!
feof($fp))
{
    echo
fread($fp, 65536);
   
flush(); // this is essential for large downloads

fclose($fp);
?>
up
1
jp at webgraphe dot com
10 years ago
A call to session_write_close() before the statement

<?php
    header
("Location: URL");
    exit();
?>

is recommended if you want to be sure the session is updated before proceeding to the redirection.

We encountered a situation where the script accessed by the redirection wasn't loading the session correctly because the precedent script hadn't the time to update it (we used a database handler).

JP.
up
1
Cody G.
3 years ago
After lots of research and testing, I'd like to share my findings about my problems with Internet Explorer and file downloads.

  Take a look at this code, which replicates the normal download of a Javascript:

<?php
if(strstr($_SERVER["HTTP_USER_AGENT"],"MSIE")==false) {
 
header("Content-type: text/javascript");
 
header("Content-Disposition: inline; filename=\"download.js\"");
 
header("Content-Length: ".filesize("my-file.js"));
} else {
 
header("Content-type: application/force-download");
 
header("Content-Disposition: attachment; filename=\"download.js\"");
 
header("Content-Length: ".filesize("my-file.js"));
}
header("Expires: Fri, 01 Jan 2010 05:00:00 GMT");
if(
strstr($_SERVER["HTTP_USER_AGENT"],"MSIE")==false) {
 
header("Cache-Control: no-cache");
 
header("Pragma: no-cache");
}
include(
"my-file.js");
?>

Now let me explain:

  I start out by checking for IE, then if not IE, I set Content-type (case-sensitive) to JS and set Content-Disposition (every header is case-sensitive from now on) to inline, because most browsers outside of IE like to display JS inline. (User may change settings). The Content-Length header is required by some browsers to activate download box. Then, if it is IE, the "application/force-download" Content-type is sometimes required to show the download box. Use this if you don't want your PDF to display in the browser (in IE). I use it here to make sure the box opens. Anyway, I set the Content-Disposition to attachment because I already know that the box will appear. Then I have the Content-Length again.

  Now, here's my big point. I have the Cache-Control and Pragma headers sent only if not IE. THESE HEADERS WILL PREVENT DOWNLOAD ON IE!!! Only use the Expires header, after all, it will require the file to be downloaded again the next time. This is not a bug! IE stores downloads in the Temporary Internet Files folder until the download is complete. I know this because once I downloaded a huge file to My Documents, but the Download Dialog box put it in the Temp folder and moved it at the end. Just think about it. If IE requires the file to be downloaded to the Temp folder, setting the Cache-Control and Pragma headers will cause an error!

I hope this saves someone some time!
~Cody G.
up
1
nobileelpirata at hotmail dot com
7 years ago
This is the Headers to force a browser to use fresh content (no caching) in HTTP/1.0 and HTTP/1.1:

<?PHP
header
( 'Expires: Sat, 26 Jul 1997 05:00:00 GMT' );
header( 'Last-Modified: ' . gmdate( 'D, d M Y H:i:s' ) . ' GMT' );
header( 'Cache-Control: no-store, no-cache, must-revalidate' );
header( 'Cache-Control: post-check=0, pre-check=0', false );
header( 'Pragma: no-cache' );

?>
up
-1
sk89q
5 years ago
You can use HTTP's etags and last modified dates to ensure that you're not sending the browser data it already has cached.

<?php
$last_modified_time
= filemtime($file);
$etag = md5_file($file);

header("Last-Modified: ".gmdate("D, d M Y H:i:s", $last_modified_time)." GMT");
header("Etag: $etag");

if (@
strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) == $last_modified_time ||
   
trim($_SERVER['HTTP_IF_NONE_MATCH']) == $etag) {
   
header("HTTP/1.1 304 Not Modified");
    exit;
}
?>
up
-1
Refugnic
4 years ago
My files are in a compressed state (bz2). When the user clicks the link, I want them to get the uncompressed version of the file.

After decompressing the file, I ran into the problem, that the download dialog would always pop up, even when I told the dialog to 'Always perform this operation with this file type'.

As I found out, the problem was in the header directive 'Content-Disposition', namely the 'attachment' directive.

If you want your browser to simulate a plain link to a file, either change 'attachment' to 'inline' or omit it alltogether and you'll be fine.

This took me a while to figure out and I hope it will help someone else out there, who runs into the same problem.
up
-3
Anonymous
5 years ago
I just want to add, becuase I see here lots of wrong formated headers.

1. All used headers have first letters uppercase, so you MUST follow this. For example:

Location, not location
Content-Type, not content-type, nor CONTENT-TYPE

2. Then there MUST be colon and space, like

good: header("Content-Type: text/plain");
wrong: header("Content-Type:text/plain");

3. Location header MUST be absolute uri with scheme, domain, port, path, etc.

good: header("Location: http://www.example.com/something.php?a=1");

4. Relative URIs are NOT allowed

wrong:  Location: /something.php?a=1
wrong:  Location: ?a=1

It will make proxy server and http clients happier.
up
-5
jamie
5 years ago
The encoding of a file is discovered by the Content-Type, either in the HTML meta tag or as part of the HTTP header. Thus, the server and browser does not need - nor expect - a Unicode file to begin with a BOM mark. BOMs can confuse *nix systems too. More info at http://unicode.org/faq/utf_bom.html#bom1

On another note: Safari can display CMYK images (at least the OS X version, because it uses the services of QuickTime)
up
-4
Anonymous
2 months ago
This is a simple function that you can use in many places if you need redirections:

<?php
function redirect($link=false){
if(!empty(
$link))
    if(!
headers_sent())
        return
header('Location: '.trim($link);
    else die(
'ERROR: Header data not send! Redirecting page is impossible! Contact System Administrator!');
else return
false;
}

// EXAMPLE:
redirect("http://www.php.net")
?>
up
-4
this dot person at joaocunha dot eti dot br
4 years ago
AVOID ZERO BYTE ORDER MARK!

Header MUST be sent before EVERYTHING in the page. Even a single space will break your script. In my case, there was BOM setted in the encoding, so I opened the file with notepad++ and set the encoding to UTF-8 (no BOM) and voila, everything is working great now.
up
-9
cedric at gn dot apc dot org
3 years ago
Setting a Location header "returns a REDIRECT (302) status code to the browser unless the 201 or a 3xx status code has already been set".  If you are sending a response to a POST request, you might want to look at RFC 2616 sections 10.3.3 and 10.3.4.   It is suggested that if you want the browser to immediately GET the resource in the Location header in this circumstance, you should use a 303 status code not the 302 (with the same link as hypertext in the body for very old browsers).  This may have (rare) consequences as mentioned in bug 42969.
up
-5
Jamesb
5 years ago
Here is a php script I wrote to stream a file and crypt it with a xor operation on the bytes and with a key :

The encryption works very good but the speed is decrease by 2, it is now 520KiB/s. The user is now asked for a md5 password (instead of keeping it in the code directly). There is some part in French because it's my native language so modify it as you want.

<?php
// Stream files and encrypt the data on-the-fly

// Settings
// -- File to stream
$file = "FILE_out";
// -- Reading buffer
$bufferlength = 3840;
// -- Key in hex
//$keychar = "9cdfb439c7876e703e307864c9167a15";

// Function: Convertion hex key in a string into binary
function hex2bin($h) {
    if (!
is_string($h)) return null;
   
$r = array();
    for (
$a=0; ($a*2)<strlen($h); $a++) {
       
$ta = hexdec($h[2*$a]);
       
$tb = hexdec($h[(2*$a+1)]);
       
$r[$a] = (int) (($ta << 4) + $tb);
    }
    return
$r;
}

// Function to send the auth headers
function askPassword($text="Enter the password") {
   
header('WWW-Authenticate: Basic realm="'. utf8_decode($text) .'"');
   
header('HTTP/1.0 401 Unauthorized');
    return
1;
}

// Key is asked at the first start
if (!isset($_SERVER['PHP_AUTH_PW'])) {
   
askPassword();
    echo
"Une clé est nécessaire !<br />";
    exit;
}
// Get the key in hex
$keychar = $_SERVER['PHP_AUTH_PW'];

// Convert key and set the size of the key
$key = hex2bin($keychar);
$keylength = count($key);
// Teste si la clé est valide en hex
if ($key == "" || $keylength <= 4) {
   
askPassword("Clé incorrecte !");
   
//echo "Clé incorrecte !<br />";
   
exit();
}
// Teste si la clé est de longueur d'une puissance de 2
if ( ($keylength%2) != 0) {
   
askPassword("Clé de longueur incorrecte (multiple de 2 uniquement)");
   
//echo "Clé de longueur incorrecte (puissance de 2 uniquement)<br />";
   
exit();
}

// Headers
header("Content-Type: application/octet-stream; ");
header("Content-Transfer-Encoding: binary");
header("Content-Length: " . filesize($file) ."; ");
header("filename=\"".$file."\"; ");
flush(); // this doesn't really matter.

// Opening the file in read-only
$fp = fopen($file, "r");
while (!
feof($fp))
{
   
// Read a buffer size of the file
   
$buffer = fread($fp, $bufferlength);
   
$j=0;
    for (
$i=0; $i < $bufferlength; $i++) {
       
// The key is read in loop to crypt the whole file
       
if ($i%$keylength == 0) {
           
$j=0;
        }
       
// Apply a xor operation between the key and the file to crypt
        // This operation eats a lots of CPU time (Stream at 1MiB/s on my server; Intel E2180)
       
$tmp = pack("C", $key[$j]);
       
$bufferE = ( $buffer[$i]^$tmp); // <==== Le fameux XOR
       
        /*
        echo "<br />key[".$j."]: ";
        var_dump($tmp);
        echo "<br />buffer[".$i."]: ";
        var_dump($buffer[$i]);
        echo "<br />bufferE: ";
        var_dump($bufferE);
        echo "<br />";
        //*/
       
        // Send the encrypted data
       
echo $bufferE;
       
// Clean the memory
       
$bufferE = "";
       
$j++;
    }
   
$buffer = "";
   
flush(); // this is essential for large downloads
    /*
    fclose($fp);
    exit();
    //*/
}
// Close the file and it's finished
fclose($fp);

?>
up
-4
dev at omikrosys dot com
4 years ago
Just to inform you all, do not get confused between Content-Transfer-Encoding and Content-Encoding

Content-Transfer-Encoding specifies the encoding used to transfer the data within the HTTP protocol, like raw binary or base64. (binary is more compact than base64. base64 having 33% overhead).
Eg Use:- header('Content-Transfer-Encoding: binary');

Content-Encoding is used to apply things like gzip compression to the content/data.
Eg Use:- header('Content-Encoding: gzip');
To Top