headers_list
very handy function!
When working with GD I made something like:
<?php
class image{
/**
* show
* sends image to browser and destroy the resource if headers not sent.
* use php constants IMAGETYPE_GIF, IMAGETYPE_JPEG, IMAGETYPE_PNG
*
* @final
* @static
* @access public
* @param resource $resource
* @param int $type
*/
final static public function show($resource, $type){
if(!headers_sent()){
header('Cache-control: private');
switch($type){
case IMAGETYPE_GIF : header('Content-type: image/gif');
header('Content-Disposition: filename='.basename(__FILE__).'.gif');
imagegif($resource);
break;
case IMAGETYPE_JPEG : header('Content-type: image/jpeg');
header('Content-Disposition: filename='.basename(__FILE__).'.jpg');
imagejpeg($resource, NULL, 99);
break;
case IMAGETYPE_PNG : header('Content-type: image/png');
header('Content-Disposition: filename='.basename(__FILE__).'.png');
imagepng($resource, NULL, 0, NULL);
break;
}
imagedestroy($resource);
exit;
}
}
}
?>
This way if you are debugging... and flush output... you will not get the endless list of headers allready send errors...
Hope it's helpfull... ;)
headers_sent
(PHP 4, PHP 5)
headers_sent — Prüft, ob oder wo die Header bereits gesendet wurden
Beschreibung
bool headers_sent
([ string &$file
[, int &$line
]] )
Prüft, ob oder wo die Header bereits gesendet wurden.
Sobald der Header-Block gesendet wurde, können Sie keine weiteren Header-Zeilen mit der Funktion header() hinzufügen. Mittels dieser Funktion können Sie aber zumindest Fehlermeldungen bezüglich der HTTP-Header vermeiden. Eine andere Möglichkeit ist die Verwendung von Output Buffering.
Parameter-Liste
- file
-
Sind die optionalen Parameter file und line angegeben, schreibt headers_sent() den PHP-Dateinamen und die Zeilennummer, an denen die Ausgabe begann, in die Variablen file und line .
- line
-
Die Zeilennummer, an der die Ausgabe begann.
Rückgabewerte
headers_sent() gibt FALSE zurück, wenn noch keine HTTP-Header gesendet wurden, ansonsten TRUE.
ChangeLog
| Version | Beschreibung |
|---|---|
| 4.3.0 | Die optionalen Parameter file und line wurden eingeführt. |
Beispiele
Beispiel #1 Beispiel zur Verwendung von headers_sent()
<?php
// Wenn keine Header gesendet wurden, sende einen
if (!headers_sent()) {
header ('Location: http://www.example.com/');
exit;
}
// Ein Beispiel für den Einsatz der seit PHP 4.3.0 verfügbaren optionalen
// Parameter file und line. Beachten Sie, dass $filename und $linenum für
// einen späteren Einsatz übergeben werden.
// Weisen Sie ihnen davor keine Werte zu.
if (!headers_sent($filename, $linenum)) {
header ('Location: http://www.example.com/');
exit;
// Wahrscheinlich wollen Sie hier eine Fehlermeldung auslösen
} else {
echo "Header bereits gesendet in $filename in Zeile $linenum\n" .
"Redirect nicht moeglich, klicken Sie daher statt dessen <a " .
"href=\"http://www.example.com\">diesen Link</a> an\n";
exit;
}
?>
Siehe auch
- ob_start()
- trigger_error()
- headers_list()
- header() for a more detailed discussion of the matters involved.
add a note
User Contributed Notesheaders_sent
loaded67 at hotmail dot com
17-Feb-2008 10:54
17-Feb-2008 10:54
Anonymous
12-Feb-2008 12:33
12-Feb-2008 12:33
I used $file from headers_sent() to determine if output has started rather than if headers have started to be sent; because the output hasn't started in between headers. This was to determine how long the xml serializer was taking to render output in my project.
<?php
# if debugging then...
DEBUG && register_shutdown_function( 'timer::comment' );
abstract class timer {
# I would post the rest of the class, however it is too long.
# Use some imagination ;D
#
# ...
#
public static function comment() {
headers_sent( $file );
if ( $file )
print( '<!-- render time="' . timer::stop() . '" /-->' . LINEBREAK );
}
}
?>
vasnake at gmail dot com
22-Jul-2007 03:55
22-Jul-2007 03:55
In my case, when I install PHP 5.2.1 in CGI mode under Apache 2.2.3 (on windows 2003 SP2),
function sent_headers() always return false. flash(), ob_end_flash(), so on... no matter.
I suppose, Apache buffering all PHP output until exit()
collectours at free dot fr
18-Jun-2007 02:32
18-Jun-2007 02:32
In response to K.Tomono and alexrussell101 at gmail dot com :
Yes,
headers_sent() will return false, even if you sent something to the ouptut using print() or header() , if output_buffering is different from Off in you php.ini, and the length of what you sent does not exceed the size of output_buffering.
To test it, try this code with these values in php.ini
1) output_buffering=32
2) output buffering = 4096
[code]
<?php
echo "Yo<br />";
echo "Sent:",headers_sent(),"<br />";
echo "enough text to feed the buffer until it overflows ;-)<br />";
echo "Sent:",headers_sent(),"<br />";
?>
[/code]
then put
3) output buffering = Off
and try this code
[code]
<?php
echo "Yo<br />";
echo "Sent:",headers_sent(),"<br />";
?>
[/code]
which will this time unconditionnally say that headers were sent.
This is noticed in php.ini comment :
"Output buffering allows you to send header lines (including cookies) even after you send body content, in the price of slowing PHP's output layer a bit."
Note : This is completly independant of implicit_flush tuning.
kamermans at teratechnologies dot net
21-Aug-2006 01:24
21-Aug-2006 01:24
If you are using output buffering and you use the flush() command ANYWHERE headers_sent() will return true - even if the buffer is seemingly empty.
Jakob B.
07-Jan-2006 03:03
07-Jan-2006 03:03
<?php
function redirect($filename) {
if (!headers_sent())
header('Location: '.$filename);
else {
echo '<script type="text/javascript">';
echo 'window.location.href="'.$filename.'";';
echo '</script>';
echo '<noscript>';
echo '<meta http-equiv="refresh" content="0;url='.$filename.'" />';
echo '</noscript>';
}
}
redirect('http://www.google.com');
?>
trevize (shtrudel) gmail.com
30-Nov-2005 06:43
30-Nov-2005 06:43
Note that in IIS (or at least the version that comes with W2K server), the server seems to do some buffering, so even if you output someting or cause a warning, the value of headers_sent() may be false because the headers haven't been sent yet.
So it's not a safe way to know if warnings have been encountered in your script.
php [at] barryhunter [.] co [.] uk
09-Sep-2005 03:42
09-Sep-2005 03:42
In responce to: Terry 11-Feb-2005 03:58
if PHP is run as a Module, then it will behave as you describe
However if PHP is run as a CGI then it will be behave like Perl, (which uses CGI unless its mod_perl), as this is a CGI behaviour.
See http://ppewww.ph.gla.ac.uk/~flavell/www/perlcgifaq.html
alexrussell101 at gmail dot com
01-Sep-2005 03:31
01-Sep-2005 03:31
To K.Tomono:
Headers are not sent as soon as you call the header() function. They are only sent as soon as some body content (i.e. HTML via echo or escaping from PHP parsing mode) is reached (or, like you did, you send a flush.) Thus after calling header a few times at the beginning they are still unsent and when you call headers_sent() it knows they haven't been sent and reports so. Only when the script ends or you output from content do all the headers so far send.
I think you misunderstood the way they are done and hopefully this should clear a few things up for you.
mark at dreamjunky dot com
28-Jun-2005 09:56
28-Jun-2005 09:56
In case this comes up with anyone else, you might trigger headers to be sent if you have a PHP file with extra space after the closing ?>. In particular, if you include that file at the top of your main script, it will cause headers to send, followed by the space after the ?> in your included script. In short, make sure you don't have any space trailing your final ?>.
K.Tomono
21-Apr-2005 10:24
21-Apr-2005 10:24
[code]
<?php
header("Cache-Control: private, must-revalidate, max-age=3600, post-check=3600, pre-check=3600");
////header("Last-Modified: " . gmdate("D, d M Y H:i:s",getlastmod())." GMT");
////ini_set("last_modified","1");
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
flush(); // <= (*1)
...
if (!headers_sent()) {
header('Content-Type:text/html; charset='._CHARSET);
header('Expires: Mon, 26 Jul 1997 05:00:00 GMT');
//header('Last-Modified: '.gmdate('D, d M Y H:i:s').' GMT');
header('Cache-Control: private, no-cache');
header('Pragma: no-cache');
}
...
?>
[/code]
headers_sent() does not evaluate it as true, unless the flush()(*1) has been done.
It seems that it does not mean header was sent unless a header output is taken
out to the exterior of PHP.
Apache 2.0.53 (prefork)
PHP 5.0.3 (server module)
... And XOOPS 2.0.9.2
I had seldom paid attention to flush() on PHP which is not C.
However, it might have been a required thing.
[pre]
$ curl --cookie PHPSESSID=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX -i \
"http ://myhost.mydomain/xoops/modules/test.php?i=1" | less
% Total % Received % Xferd Average Speed Time Curr.
Dload Upload Total Current Left Speed
0 0 0 0 0 0 0 0 --:--:-- 0:00:00 --:--:-- 0
HTTP/1.1 200 OK
Date: Fri, 22 Apr 2005 05:00:11 GMT
Server: Apache
X-Powered-By: PHP/5.0.3
Set-Cookie: PHPSESSID=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX; path=/
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: private, must-revalidate, max-age=3600, post-check=3600, pre-check=3600
Pragma: no-cache
Last-Modified: Fri, 22 Apr 2005 05:00:11 GMT
Transfer-Encoding: chunked
Content-Type: text/html
[/pre]
(*)"http :" is "http:" in fact.
Terry
10-Feb-2005 07:58
10-Feb-2005 07:58
For programmers used to Perl, note that sending a relative 'Location:' header sends a redirect to the browser in PHP, unlike Perl which will attempt to call relative URLs using an internal subrequest and return that page to the browser without redirecting. If you want to do the same trick in PHP, use include() or virtual().
php at fufachew dot REMOVEME dot com
28-Feb-2004 11:26
28-Feb-2004 11:26
RE: antti at haapakangas dot net's post
I've changed the code so $_SERVER['SERVER_NAME'] is used if $_SERVER['HTTP_HOST'] is not set. $_SERVER['SERVER_NAME'] doesn't meet my needs, but I suppose it's good to fall back on it. I've also fixed a problem in the meta refresh line - it was missing the "url=" part of the content attribute.
<?php
function server_url()
{
$proto = "http" .
((isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] == "on") ? "s" : "") . "://";
$server = isset($_SERVER['HTTP_HOST']) ?
$_SERVER['HTTP_HOST'] : $_SERVER['SERVER_NAME'];
return $proto . $server;
}
function redirect_rel($relative_url)
{
$url = server_url() . dirname($_SERVER['PHP_SELF']) . "/" . $relative_url;
if (!headers_sent())
{
header("Location: $url");
}
else
{
echo "<meta http-equiv=\"refresh\" content=\"0;url=$url\">\r\n";
}
}
?>
antti at haapakangas dot net
28-Jan-2004 12:39
28-Jan-2004 12:39
Re: php at fufachew dot com
That's a nice example how to implement Location header in a correct way (using absoluteURI). 95% of the scripts I have seen just use relativeURI which is wrong. Some browsers, for example lynx, actually notify user about incomplete Location headers. However it might be safer to use $_SERVER['SERVER_NAME'] instead of $_SERVER['HTTP_HOST']. Host header is a HTTP/1.1 feature and you can not count on that if you want to be interoperable with HTTP/1.0 implementations.