Bug #80558 [Com]: Apache ErrorDocument subrequest fails horribly
Edit report at https://bugs.php.net/bug.php?id=80558&edit=1
ID: 80558
Comment by: rtrtrtrtrt at dfdfdfdf dot dfd
Reported by: problembug at speed dot 1s dot fr
Summary: Apache ErrorDocument subrequest fails horribly
Status: Open
Type: Bug
Package: Apache related
Operating System: Linux
PHP Version: 7.4.13
Block user comment: N
Private report: N
New Comment:
just put ob_start() as first line of your error-script and/or remove linebreaks after ?> which is
the reason for *not* use ?> at the end of the file
for sure not a php bug
Previous Comments:
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[2020-12-28 16:44:10] problembug at speed dot 1s dot fr
Description:
------------
Reproducible on Amazon Linux, Slackware and others with various combinations of (recent) PHP and
Apache. When httpd.conf is configured with an ErrorDocument to a PHP script and an error is
deliberately introduced with a faulty header, the mere presence of a flush() changes the graceful
error handling (via a subrequest) in to a confusing and bizarre situation that introduces secondary
bugs.
These include:
o PHP no longer honours previous require_once include guard
o Apache not sending back any output to the client
o Misleading messages in the PHP error log about other modules
o Misleading messages in the PHP error log about ini_set (?) which is never used
o PHP error log messages repeated multiple times
The presence of a single flush() changes the graceful error handling ($test = 2) in to a confusing
mess ($test = 3) and introduces seemingly unrelated bugs.
Steps to reproduce:
1. Edit an Apache VirtualHost config in to include the following:
ErrorDocument 500 /error.php
2. Place the 3 attached scripts in the VirtualHost's DocumentRoot:
test.php error.php library.php
3. Restart Apache
4. Access https://somesite/test.php
5. Alter test.php to try $test = 2 and $test = 3
6. Observe all the unexpected and secondary problems the flush() introduces
Test script:
---------------
https://pastebin.com/MBQEEb5Q
Expected result:
----------------
Expected result for test 3 is same as test 2:
----
PHP error log:
No new entries.
----
$ curl -i https://somesite/test.php
HTTP/1.1 500 Internal Server Error
Date: Sun, 27 Dec 2020 14:05:47 GMT
Server: Apache
Content-Type: text/html; charset=UTF-8
I will deal with a 500 error and show a pretty error message
Actual result:
--------------
Actual result for test 3:
----
PHP error log:
[27-Dec-2020 13:49:41 UTC] PHP Warning: flush(): Headers already sent. You cannot change the
session module's ini settings at this time in /www/test.php on line 22
[27-Dec-2020 13:49:41 UTC] PHP Warning: flush(): Headers already sent. You cannot change the
session module's ini settings at this time in /www/test.php on line 22
[27-Dec-2020 13:49:41 UTC] PHP Warning: flush(): Headers already sent. You cannot change the
session module's ini settings at this time in /www/test.php on line 22
[27-Dec-2020 13:49:41 UTC] PHP Warning: flush(): Headers already sent. You cannot change the
session module's ini settings at this time in /www/test.php on line 22
[27-Dec-2020 13:49:41 UTC] PHP Fatal error: Cannot redeclare foo() (previously declared in
/www/library.php:4) in /www/library.php on line 4
----
$ curl -i https://somesite/test.php
curl: (52) Empty reply from server
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Edit this bug report at https://bugs.php.net/bug.php?id=80558&edit=1
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