[Tickets #7851] Re: "Headers already sent" caused by usage of flush()

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Ticket URL: http://bugs.horde.org/ticket/7851
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  Ticket             | 7851
  Updated By         | thomas at gelf.net
  Summary            | "Headers already sent" caused by usage of flush()
  Queue              | DIMP
  Version            | 1.1.1
  Type               | Bug
  State              | Feedback
  Priority           | 2. Medium
  Milestone          |
  Patch              |
  Owners             |
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thomas at gelf.net (2009-01-16 04:17) wrote:

>>> Cannot modify header information - headers already sent in Unknown
>>> on line 0
> This will happen if you have extra space at the top of one of your
> config files.

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.

> 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 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?