ID: 32414
User updated by: d dot geels at grape dot ru
Reported By: d dot geels at grape dot ru
Status: Open
Bug Type: Documentation problem
Operating System: any
PHP Version: 4.3.10, also 5
New Comment:
The problem is that session_start() tries to send headers, but it must
not.
Try 'curl -v <url to above example>' and just call function a() at the
end, without registering shutdown function, you'll see, that
session_start() doesn't send any headers if second call to
session_cache_limiter has parameter 'none'. So, why does it complain,
when called from shutdown function? That is the bug actually.
Previous Comments:
------------------------------------------------------------------------
[2005-03-22 22:56:05] [EMAIL PROTECTED]
This is actually just documentation problem:
You can't send any headers from a register_shutdown_function() call.
Or use any functions in such function that might send headers..such as
almost any session function.
------------------------------------------------------------------------
[2005-03-22 18:46:42] d dot geels at grape dot ru
Tiny example, that always reproduces the bug.
<?
ini_set('session.use_cookies', 0);
session_id('1234');
session_cache_limiter('public');
session_start();
session_write_close();
?>
text
<?
function a(){
session_cache_limiter('none');
session_start();
session_write_close();
}
register_shutdown_function('a');
?>
If just call a() at the end -- no warnings, if a() called at shutdown
-- warning issued.
------------------------------------------------------------------------
[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
