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headers_sent (PHP 3 >= 3.0.8, PHP 4, PHP 5) headers_sent -- Проверяет отправлены ли HTTP-заголовки клиенту и, если отправлены, то где Описаниеbool headers_sent ( [string &file [, int &line]] )
headers_sent() возвращает FALSE, если HTTP заголовки еще
не были отправлены клиенту, и TRUE в противоположном случае. Если были
указаны необязательные параметры file и line,
headers_sent() вернет имя файла и номер строки, где был начат вывод
данных в переменные file и
line соответственно.
Вы не можете добавить новые заголовки при помощи функции
header(), если заголовки уже были отправлены клиенту.
Использование данной функции позволит вам
лишь избежать сообщений об ошибках, связанных повторной отправкой
HTTP-заголовков.
Другой выход - использовать буферизацию вывода.
Замечание:
Необязательные параметры file и line
были добавлены в PHP 4.3.0.
Пример 1. Пример использования headers_sent() |
<?php
if (!headers_sent()) {
header('Location: http://www.example.com/');
exit;
}
if (!headers_sent($filename, $linenum)) {
header('Location: http://www.example.com/');
exit;
} else {
echo "Заголовки уже отправлены в $filename на строке $linenum\n" .
"Редирект невозможен, пожалуйста нажмите <a " .
"href=\"http://www.example.com\">Здесь</a> самостоятельно\n";
exit;
}
?>
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Смотрите также функции ob_start(), trigger_error(),
и header() для более подробного обсуждения затронутых
вопросов.
headers_sent
rajnesh at gmail dot com
24-Feb-2006 10:19
headers_sent() will return FALSE if no HTTP headers have already been sent or TRUE otherwise. If the optional file and line parameters are set, headers_sent() will put the PHP source file name and line number where output started in the file and line variables.
You can't add any more header lines using the header() function once the header block has already been sent. Using this function you can at least prevent getting HTTP header related error messages. Another option is to use Output Buffering.
Note: The optional file and line parameters where added in PHP 4.3.0.
Jakob B.
07-Jan-2006 03:03
<?php
function redirect($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
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.
alexrussell101 at gmail dot com
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
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
[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") . " GMT");
flush(); ...
if (!headers_sent()) {
header('Content-Type:text/html; charset='._CHARSET);
header('Expires: Mon, 26 Jul 1997 05:00:00 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
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
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
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.
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