Changes have been made in Git for this ticket:

Fix notices with certain output buffer configurations 
(Valentin.Vidic@CARNet.hr, Bug #7851).

http://git.horde.org/diff.php/imp/docs/CHANGES?rt=horde-git&r1=19c0155646f0ccddf91d0f33e237b035d401f075&r2=73d6cbe80185537f3845952d00e351a4a1b26b03
http://git.horde.org/diff.php/imp/lib/Dimp.php?rt=horde-git&r1=76c1c091e8c027ce77dea8d76ceb2fef5d4cecb4&r2=73d6cbe80185537f3845952d00e351a4a1b26b03
http://git.horde.org/diff.php/kronolith/lib/Kronolith.php?rt=horde-git&r1=2d61ecac5bcd544a6ea4e9c0cc1200f6e6b2d283&r2=73d6cbe80185537f3845952d00e351a4a1b26b03

Changes have been made in CVS for this ticket:

Fix notices with certain output buffer configurations 
(Valentin.Vidic@CARNet.hr, Bug #7851).
http://cvs.horde.org/diff.php/dimp/docs/CHANGES?rt=horde&r1=1.69.2.84&r2=1.69.2.85&ty=u
http://cvs.horde.org/diff.php/dimp/lib/DIMP.php?rt=horde&r1=1.110.2.39&r2=1.110.2.40&ty=u

I'm also seeing a lot of 'headers already sent in Unknown on line 0' 
in apache error logs. However the manual for flush says: 
http://php.net/manual/en/function.flush.php

flush() may not be able to override the buffering scheme of your web 
server and it has no effect on any client-side buffering in the 
browser. It also doesn't affect PHP's userspace output buffering 
mechanism. This means you will have to call both ob_flush() and 
flush() to flush the ob output buffers if you are using those.

And if I add an ob_flush() call before flush() the error message goes 
away. Patch is attached.

Sounds like looking for UTF-8 BOMs at the beginning of your config 
files or the beginning of the translations (?) might be the thing to 
try next here.

Googling I also stumbled over this issue, it lead me to "grep -r flush .",

and helped me to easily "solve" my problem. But I still have no idea

how UTF8 BOM's could cause this issue?! If so, this must be a PHP bug,

is this assumption correct? Shall I search for UTF8-Strings in my config

files??



I still have no clue :-( Thank you for your patience!!

Not necessarily.



Anyway, it might be this similar issue (w/UTF8 BOM's):

http://trac.roundcube.net/ticket/1483926

No, I'm pretty sure I haven't - in that case it would tell me file and line

number where the output started. And even without the flush notices

would still be there.
There is nothing related in my Horde log - but every day (running in

production since four days right now) there have been thousands of

this strange line in my syslog, I'm logging all PHP errors and warnings.



In our beta phase I've had PHP output Notices to the browser, but I

never noticed them, and I still have no idea, WHY they appear. It

could also be related to some strange PHP bug. But fact is: removing

the flush solved it, no more such notice so far.



As soon as time allows me to do so, I'll try to do some more tests.

If someone else running DIMP in a production environment with more

than a few hundred users, preferrably with same / similar PHP version

and APC enabled, could enable logging for PHP errors and tell me

wheter he / she is also seeing this errors, that would be a great help.



For sure it could also be related to our personalisation / customization

work, we strongly modified DIMP's appearance - but (repeating myself)

if I really would have some prior output in my code or config files, PHP

would tell me WHERE output has started.



This one is really strange, I've neve before seen something similar.

Anyone else?

This will happen if you have extra space at the top of one of your 
config files.
That is correct - DIMP will catch any unexpected input at the very end 
of processing and toss it - but will also this unexpected output at a 
DEBUG level to the Horde log.  So this has probably been an issue 
forever - you simply haven't seen it because you are not logging at a 
DEBUG level.

There has been added a flush() call in DIMP.php between revision 1.131

and 1.132 - causing thousands of warning lines a day in my syslog:
I'm running latest Debian Lenny, PHP 5.2.6 (untouched, from Lenny) as an

Apache Module, APC Cache enabled.



See http://cvs.horde.org/diff.php/dimp/lib/DIMP.php?r1=1.131&r2=1.132

for the exact change (not documented in CVS log).



Removing the flush()-call solves this issue, no more warnings since then.



Kind regards,

Thomas Gelf