ID: 32414
Updated by: sniper@php.net
Reported By: d dot geels at grape dot ru
-Status: Open
+Status: Feedback
Bug Type: Session related
Operating System: any
PHP Version: 4.3.10, also 5
New Comment:
Do you have 'session.auto_start' set on somewhere?
(httpd.conf, .htaccess file, php.ini..)
Previous Comments:
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[2005-03-22 18:25:12] d dot geels at grape dot ru
There is one more detail, I forgot to mention:
I couldn't kill warning message by calling @start_session() in line 45.
Is this because of warning message issued somewhere in calls from
session_start()?
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[2005-03-22 18:16:04] d dot geels at grape dot ru
Just viewd latest session.c from CVS repository. There are not much
changes between versions 4 and 5, so bug still remains in PHP 5.
Somewhere here:
static int php_session_cache_limiter(TSRMLS_D)
{
php_session_cache_limiter_t *lim;
// for some reason, this string fails
if (PS(cache_limiter)[0] == '\0') return 0;
// I cant understand all this file, but I think, problem is
// that value 'none' is not properly recognized or processed
if (SG(headers_sent)) {
char *output_start_filename =
php_get_output_start_filename(TSRMLS_C);
int output_start_lineno = php_get_output_start_lineno(TSRMLS_C);
if (output_start_filename) {
php_error_docref(NULL TSRMLS_CC, E_WARNING, "Cannot send session
cache limiter - headers already sent (output started at %s:%d)",
output_start_filename, output_start_lineno);
} else {
php_error_docref(NULL TSRMLS_CC, E_WARNING, "Cannot send session
cache limiter - headers already sent");
}
return -2;
}
for (lim = php_session_cache_limiters; lim->name; lim++) {
if (!strcasecmp(lim->name, PS(cache_limiter))) {
lim->func(TSRMLS_C);
return 0;
}
}
return -1;
}
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[2005-03-22 17:38:57] d dot geels at grape dot ru
Description:
------------
The problem described already in user contributed noted in
documentation. Strange, that it is not yet fixed...
Also problem mentioned in http://bugs.php.net/bug.php?id=11213
==================================
laacz at laacz dot lv (28-Oct-2004 03:37)
If You are not using cookies to store session_id's, that does not mean,
that session_start() will not send any headers at all. It still sends
cache controlling information to user. For example:
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0,
pre-check=0
Pragma: no-cache
Even, if You set cache_limiter to none (via
ini_set('session.use_cookies', 0) or ini_set('session.cache_limiter',
'none')), session_start() still tries to send empty headers and that
causes error message "Cannot send session cache limiter - headers
already sent". So, use output buffering, if You need to output
something before session_start().
==================================
even session_cache_limiter('none') doesn't work
In my case, problem is that I call session_start(), then
session_write_close() in the beginning, then send data, then call
session_start(), then session_write_close() in the function, registered
on shutdown.
There are two reasons, why I do so:
1) there are several processes, that access same session (I use
md5($_SERVER['REMOTE_ADDR']) as session_id)
2) I can't buffer output at all. Amount of data is very large, it is a
file being downloaded. It must be sent ASAP.
Reproduce code:
---------------
if(!empty($_SERVER['HTTP_RANGE'])){
$sid = md5($_SERVER['REMOTE_ADDR']);
ini_set('session.use_cookies', 0);
session_cache_limiter('public'); // for IE "Open" bug
session_id($sid);
session_start(); //this one starts normally
//check, if this download thread is permitted or not
if(!empty($_SESSION['file_'.$file_id]) && $_SESSION['file_'.$file_id]
>= MAX_DOWNLOAD_THREADS){
header('HTTP/1.1 403 Forbidden', true, 403);
exit;
}elseif(!isset($_SESSION['file_'.$file_id]))
$_SESSION['file_'.$file_id] = 0;
$_SESSION['file_'.$file_id]++;
session_write_close();
//close session ASAP, because else other processes would be blocked
//this function will decrement threads counter...
function decrementCounter($sid, $file_id)
{
//this must help us evade "Warning: session_start(): Cannot send
session cache limiter - headers already sent"
session_cache_limiter('none');
session_id($sid);
session_start(); // this is line #45
//decrement threads counter
$_SESSION['file_'.$file_id]--;
session_write_close();
//close session ASAP
}
//... when script finished
register_shutdown_function('decrementCounter', $sid, $file_id);
}
Expected result:
----------------
No warnings in log file.
Actual result:
--------------
[Tue Mar 22 18:32:08 2005] [error] PHP Warning: session_start():
Cannot send session cache limiter - headers already sent (output
started at /home/httpd/pantech/htdocs/file.php:144) in
/home/httpd/pantech/htdocs/file.php on line 45
reproduced always, when user downloading a file
line 144 sends data to client:
echo fread( $fp, $size > READ_BLOCK_SIZE ? READ_BLOCK_SIZE : $size );
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Edit this bug report at http://bugs.php.net/?id=32414&edit=1