FS#1919 gzip_output = 1 leads to "Cannot modify header information - headers already sent"

CSS, XHTML, JS, Browsers

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  2010-03-14 sebastiw

  When the option gzip_output is enabled, you get the following error in apaches error.log for every viewed page:
  
  PHP Warning:  Cannot modify header information - headers already sent in Unknown on line 0
  
  which is especially confusing because of the "Unknown on line 0"
  Besides that error in the error.log I have not noticed any other problems.
  
  I think it should be a problem even on a fresh install of Dokuwiki. If you cannot reproduce it, I can give you more information...
• 

  2010-03-15 sebastiw

  I forgot to include the Links how I found out about the solution to disable the gzip option:
  what really helped was: http://stackoverflow.com/questions/622192/php-warning-headers-already-sent-in-unknown
  especially the second answer. I don't know if that, and the linked bugreport there: http://bugs.php.net/bug.php?id=9031 are really the cause (the Bug is really really old), but maybe it is a hint :)
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  2010-06-07 andi

  What PHP version are you using? Is gzip compression maybe already enabled in either your php.ini or in your webserver?
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  2010-06-07 sebastiw

  Its a debian stable system with the php version of debian stable (PHP Version 5.2.6-1+lenny8 including suhosin patch 0.9.6.2) installed as module for apache2.
  
  in php.ini:
  zlib.output_compression = Off
  (is there any other option for "gzip compression"?)
  
  I did not find any option related to gzip compression in the apache conf files... so probably it is not enabled. What would the name of that option be?
  
  Regards
  Sebastian  
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  2010-10-02 andi

  Usually mod_gzip or mod_deflate are used for that. Can you check again? Are there maybe any other PHP configs that are autoprepended that might cause the error?
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  2010-11-19 Tanguy

  Another Debian user had the same problem, cf. bug report http://bugs.debian.org/603937 .
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  2011-03-04 andi

  AFAIK the standard Debian Apache 2 setup ads mod_deflate with compression for text/html. Using PHP's gzip compression handler is unnecessary then and probably the cause for this problem.