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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
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.
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.
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:
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.
&?php//&We'll&be&outputting&a&PDFheader('Content-Type:&application/pdf');//&It&will&be&called&downloaded.pdfheader('Content-Disposition:&&filename="downloaded.pdf"');//&The&PDF&source&is&in&original.pdfreadfile('original.pdf');?&
Exemplo #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:
&?phpheader("Cache-Control:&no-cache,&must-revalidate");&//&HTTP/1.1header("Expires:&Sat,&26&Jul&:00&GMT");&//&Date&in&the&past?&
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,
the session.cache_limiter configuration
setting can be used to automatically generate the correct
caching-related headers when sessions are being used.
Session ID is not passed with Location header even if
enabled. It must by passed manually using SID
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.
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
A quick way to make redirects permanent or temporary is to make use of the $http_response_code parameter in header().&?phpheader("Location: /foo.php",TRUE,301);header("Location: /foo.php",TRUE,302);header("Location: /foo.php");header("Location: /foo.php",TRUE,303);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.
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& & $fn = '/test/foo.png';& & $headers = apache_request_headers(); & & if (isset($headers['If-Modified-Since']) && (strtotime($headers['If-Modified-Since']) == filemtime($fn))) {& & & & header('Last-Modified: '.gmdate('D, d M Y H:i:s', filemtime($fn)).' GMT', true, 304);& & } else {& & & & header('Last-Modified: '.gmdate('D, d M Y H:i:s', filemtime($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. :)
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: filename=" . basename($filename));?&you should type:&?php& header("Content-Disposition: filename=\"" . basename($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
for more information. (Sorry, the site won't let me post such a long link...)
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-storeCache-control:no-cacheSee: 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
According to the RFC 6226 (), the only way to send Content-Disposition Header with encoding is:Content-Disposition:& & & & & & & & & & & & & filename*= UTF-8''%e2%82%ac%20ratesfor backward compatibility, what should be sent is:Content-Disposition:& & & & & & & & & & & & & filename="EURO rates";& & & & & & & & & & & & & filename*=utf-8''%e2%82%ac%20ratesAs a result, we should use&?php$filename = '中文文件名.exe';&& $contentDispositionField = 'Content-Disposition: '& & . sprintf('filename="%s"; ', rawurlencode($filename))& & . sprintf("filename*=utf-8''%s", rawurlencode($filename));header('Content-Type: application/octet-stream');header($contentDispositionField);readfile('file_to_download.exe');?&I have tested the code in IE6-10, firefox and Chrome.
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.&?phpheader("location: 1.html"); header("location: 2.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.&?phpheader("location: 1.html");echo "send data"; header("location: 2.html"); ?&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.&?phpob_start();header("location: 1.html"); echo "send data"; header("location: 2.html"); ob_end_flush(); ?&
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.
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. &?phpheader("Content-Disposition: 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(); $fp = fopen($file, "r"); while (!feof($fp)){& & echo fread($fp, 65536); & & flush(); }& fclose($fp); ?&
In the bottom note:&?php $uri&& = rtrim(dirname($_SERVER['REQUEST_URI']), '/\\');?&not $_SERVER['PHP_SELF']!(But the strange behaviour of dirname is a problem for URL ending by a directory without file name!)
After lots of research and testing, I'd like to share my findings about my problems with Internet Explorer and file downloads.& Take a look at this code, which replicates the normal download of a Javascript:&?php if(strstr($_SERVER["HTTP_USER_AGENT"],"MSIE")==false) {& header("Content-type: text/javascript");& header("Content-Disposition: filename=\"download.js\"");& header("Content-Length: ".filesize("my-file.js")); } else {& header("Content-type: application/force-download");& header("Content-Disposition: filename=\"download.js\"");& header("Content-Length: ".filesize("my-file.js")); } header("Expires: Fri, 01 Jan :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.
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).
Just to inform you all, do not get confused between Content-Transfer-Encoding and Content-EncodingContent-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');
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");
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 likeHTTP/1.1 200 OKServer: Apache/2.2.11 (Unix)X-Powered-By: PHP/5.2.8Date: Fri, 16 Oct :07 GMTContent-Type: text/ charset=UTF-8Connection: closeIf you call the header name with no value like so...&?php& & header( 'Content-Type:' );?&Your headers now look like this:HTTP/1.1 200 OKServer: Apache/2.2.11 (Unix)X-Powered-By: PHP/5.2.8Date: Fri, 16 Oct :07 GMTConnection: close
Saving php file in ANSI& no isuess but when saving the file in UTF-8 format for various reasons remember to save the file without any BOM ( byte-order mark) support.Otherwise you will face problem of headers not being properly sent eg. &?php header("Set-Cookie: name=user");?&Would give something like this :-Warning: Cannot modify header information - headers already sent by (output started at C:\www\info.php:1) in C:\www\info.php on line 1
The piece of code in the manual which is as follows&html&&?phpheader('Location: ');?&this will not throw a warning as the .ini settings for output buffering is by default on.to get the error you may have to change the server setting or simply add a line explicitly to close output buffering by using "ob_end_clean()" or similar
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 :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' );
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: ");
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.
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
$file = "FILE_out";
$bufferlength = 3840;
function hex2bin($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 $r;
}
function askPassword($text="Enter the password") {
& & header('WWW-Authenticate: Basic realm="'. utf8_decode($text) .'"');
& & header('HTTP/1.0 401 Unauthorized');
& & return 1;
}
if (!isset($_SERVER['PHP_AUTH_PW'])) {
& & askPassword();
& & echo "Une clé est nécessaire !&br /&";
& &
}
$keychar = $_SERVER['PHP_AUTH_PW'];
$key = hex2bin($keychar);
$keylength = count($key);
if ($key == "" || $keylength &= 4) {
& & askPassword("Clé incorrecte !");
& & exit();
}
if ( ($keylength%2) != 0) {
& & askPassword("Clé de longueur incorrecte (multiple de 2 uniquement)");
& & exit();
}
header("Content-Type: application/octet- ");
header("Content-Transfer-Encoding: binary");
header("Content-Length: " . filesize($file) ."; ");
header("filename=\"".$file."\"; ");
flush(); $fp = fopen($file, "r");
while (!feof($fp))
{
& & $buffer = fread($fp, $bufferlength);
& & $j=0;
& & for ($i=0; $i & $bufferlength; $i++) {
& & & & if ($i%$keylength == 0) {
& & & & & & $j=0;
& & & & }
& & & & $tmp = pack("C", $key[$j]);
& & & & $bufferE = ( $buffer[$i]^$tmp); echo $bufferE;
& & & & $bufferE = "";
& & & & $j++;
& & }
& & $buffer = "";
& & flush(); }
fclose($fp);
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");
& &
}
?&
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.
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: filename=..." header line.I eventually determined that my Apache installation was adding an additional header: "Vary: Host", which was throwing IE - as per 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
DO NOT PUT space between location and the colon that comes after that , // DO NOT USE THIS : header("Location : #whatever"); // -& will not work !// INSTEAD USE THIS -& header("Location: #wahtever"); // -& will work forever !
&?phpheader('Location: /target.php', true, $code) to forward user to another page:$code = 301;$code = 302; (default)$code = 303;$code = 307;?&
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 On another note: Safari can display CMYK images (at least the OS X version, because it uses the services of QuickTime)
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.}