Title: Problem: Cannot modify header information
Last modified: August 20, 2016

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# Problem: Cannot modify header information

 *  [fxkrk](https://wordpress.org/support/users/fxkrk/)
 * (@fxkrk)
 * [13 years, 7 months ago](https://wordpress.org/support/topic/problem-cannot-modify-header-information-2/)
 * Hello,
 * few days ago i`ve updated my wordpress multisite into newest version.
 * Problem is, that now i see “Cannot modify header information headers already 
   sent by (output started at /index.php:2) in /wp-content/mu-plugins/domain_mapping.
   php on line 724” when i try to see example blog on my WP multisite via “secondary”
   domain. Primary domain works fine, secondary don`t
 * Domain mapping plugin version is 0.5.4.2
 * Could you please help me?
 * [http://wordpress.org/extend/plugins/wordpress-mu-domain-mapping/](http://wordpress.org/extend/plugins/wordpress-mu-domain-mapping/)

Viewing 3 replies - 1 through 3 (of 3 total)

 *  [trejder](https://wordpress.org/support/users/trejder/)
 * (@trejder)
 * [13 years, 7 months ago](https://wordpress.org/support/topic/problem-cannot-modify-header-information-2/#post-3153791)
 * It seems, that you have read Otto’s outdated instruction. It is 2,5 year old 
   and written for an old version of this plugin. You’re using newest one.
 * Read ‘Instruction’ for this plugin again. It says in one chapter: “Illustrated
   installation instructions can be found here but you can ignore the instructions
   to place domain_mapping.php in mu-plugins”.
 * Solution to your problem should be deleting “domain_mapping.php” from “mu_plugins”
   folder or remove whole this folder. Newest version of this pluging doesn’t require
   it.
 *  Plugin Author [Ron Rennick](https://wordpress.org/support/users/wpmuguru/)
 * (@wpmuguru)
 * [13 years, 7 months ago](https://wordpress.org/support/topic/problem-cannot-modify-header-information-2/#post-3153793)
 * Moving the plugin file will not fix the error.
 * Try updating to the development version (under the developer tab on the plugin
   page).
 *  [trejder](https://wordpress.org/support/users/trejder/)
 * (@trejder)
 * [13 years, 7 months ago](https://wordpress.org/support/topic/problem-cannot-modify-header-information-2/#post-3153794)
 * I just wrote, what I saw, basing on my own experience. I too followed Otto’s 
   example, copied “domain_mapping.php” to “mu_plugins” and got exactly the same
   error message. Removing “domain_mapping.php” from “mu_plugins” solved the problem.
 * If you think, that above mentioned error has different source than placing “domain_mapping.
   php” in “mu_plugins”, then maybe this is some kind of coincidence.

Viewing 3 replies - 1 through 3 (of 3 total)

The topic ‘Problem: Cannot modify header information’ is closed to new replies.

 * ![](https://s.w.org/plugins/geopattern-icon/wordpress-mu-domain-mapping.svg)
 * [WordPress MU Domain Mapping](https://wordpress.org/plugins/wordpress-mu-domain-mapping/)
 * [Frequently Asked Questions](https://wordpress.org/plugins/wordpress-mu-domain-mapping/#faq)
 * [Support Threads](https://wordpress.org/support/plugin/wordpress-mu-domain-mapping/)
 * [Active Topics](https://wordpress.org/support/plugin/wordpress-mu-domain-mapping/active/)
 * [Unresolved Topics](https://wordpress.org/support/plugin/wordpress-mu-domain-mapping/unresolved/)
 * [Reviews](https://wordpress.org/support/plugin/wordpress-mu-domain-mapping/reviews/)

 * 3 replies
 * 3 participants
 * Last reply from: [trejder](https://wordpress.org/support/users/trejder/)
 * Last activity: [13 years, 7 months ago](https://wordpress.org/support/topic/problem-cannot-modify-header-information-2/#post-3153794)
 * Status: not resolved