Title: Cannot modify header information error – functions.php Last modified: August 20, 2016 --- # Cannot modify header information error – functions.php * Resolved [carloravelli](https://wordpress.org/support/users/carloravelli/) * (@carloravelli) * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/) * I am getting a cannot modify header information error on my functions.php, more specifically a file it’s including (which is not the issue). * `Warning: Cannot modify header information - headers already sent by (output started at /home/yc/domains/yc.keytoe.nl/public_html/wp-content/themes/yourconnector/ inc/metaboxes.php:6) in /home/yc/domains/yc.keytoe.nl/public_html/wp-includes/ pluggable.php on line 881` * Metaboxes.php is my metabox file, where I have all my code for just that. Everything works fine except when trying to save anything, I get a blank page. The save is succesful but I have to manually go back to wp-admin and that obviously isn’t how it’s supposed to work. * My metaboxes.php code is: * ``` ``` * I can’t really figure out what’s wrong. It can’t be whitespaces, checked all that. Viewing 15 replies - 1 through 15 (of 19 total) 1 [2](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/page/2/?output_format=md&replies=12) [→](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/page/2/?output_format=md&replies=12) * [Shane Gowland](https://wordpress.org/support/users/thewebatom/) * (@thewebatom) * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/#post-3154519) * 99% of the time this error is caused by whitespace in functions.php. * Try removing the closing `?>` from both metaboxes.php and functions.php. * Thread Starter [carloravelli](https://wordpress.org/support/users/carloravelli/) * (@carloravelli) * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/#post-3154525) * Doesn’t do the trick. Someone else told me it could be that add_meta_box is outputting html is messing it up, could that be it? * [Andrew Nevins](https://wordpress.org/support/users/anevins/) * (@anevins) * WCLDN 2018 Contributor | Volunteer support * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/#post-3154526) * Is `(this is line 6)` in your actual code? * Thread Starter [carloravelli](https://wordpress.org/support/users/carloravelli/) * (@carloravelli) * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/#post-3154527) * Nope, just a note to show where the 6th line is (that’s where the error starts). * Moderator [Jan Dembowski](https://wordpress.org/support/users/jdembowski/) * (@jdembowski) * Forum Moderator and Brute Squad * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/#post-3154530) * It’s almost certainly your theme but that’s easy to confirm. * Try switching to to the Twenty Eleven by using FTP or other file management and rename `themes/yourconnector` to `themes/yourconnector-old`. Then visit `http:// your-url-here/wp-admin/themes.php` page and you should be switched to the Twenty Eleven theme. * > Doesn’t do the trick. Someone else told me it could be that add_meta_box is > outputting html is messing it up, could that be it? * Shouldn’t be, that would cause a different error I think. Can you use [pastebin.com](http://pastebin.com/) and post the link to that for that entire file? Line numbers work there and the forum here does not handle code that well. * It could be your `functions.php` or it could also be your `wp-config.php` file too even though it’s not given you grief before. * [http://codex.wordpress.org/FAQ_Troubleshooting#How_do_I_solve_the_Headers_already_sent_warning_problem.3F](http://codex.wordpress.org/FAQ_Troubleshooting#How_do_I_solve_the_Headers_already_sent_warning_problem.3F) * Thread Starter [carloravelli](https://wordpress.org/support/users/carloravelli/) * (@carloravelli) * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/#post-3154536) * [http://pastebin.com/52UZYqaY](http://pastebin.com/52UZYqaY) * Not sure what switching themes is going to do, but I’ll go ahead and do that. * And I already checked that link before, whitespaces are not the problem, I’m pretty sure of that. wp-config is clean as it came in the package, only thing I did was turn debug on. * Moderator [keesiemeijer](https://wordpress.org/support/users/keesiemeijer/) * (@keesiemeijer) * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/#post-3154537) * > Everything works fine except when trying to save anything * Do you print or echo something out in your metabox code when saving a post? * example from: [http://codex.wordpress.org/Function_Reference/add_meta_box#Example](http://codex.wordpress.org/Function_Reference/add_meta_box#Example) * ``` /* Do something with the data entered */ add_action( 'save_post', 'myplugin_save_postdata' ); ``` * Can you show us the code where you save your metabox data? * Thread Starter [carloravelli](https://wordpress.org/support/users/carloravelli/) * (@carloravelli) * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/#post-3154538) * > Can you show us the code where you save your metabox date? * Check my previous comment, that’s the metaboxes.php file that has everything. * Moderator [Jan Dembowski](https://wordpress.org/support/users/jdembowski/) * (@jdembowski) * Forum Moderator and Brute Squad * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/#post-3154541) * > Not sure what switching themes is going to do, but I’ll go ahead and do that. * It’s just part of the check list and will help confirm where the problem _may_ be. * Thread Starter [carloravelli](https://wordpress.org/support/users/carloravelli/) * (@carloravelli) * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/#post-3154543) * A succesful save with twentyeleven, so that’s my theme’s issue right? Weird thing is it this issue came out of nowhere. * Moderator [Jan Dembowski](https://wordpress.org/support/users/jdembowski/) * (@jdembowski) * Forum Moderator and Brute Squad * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/#post-3154545) * I just checked, this is a duplicate post you’ve created. * [http://wordpress.org/support/topic/unusual-issues-with-both-wordpress-and-my-theme-wp-admin-related?replies=2](http://wordpress.org/support/topic/unusual-issues-with-both-wordpress-and-my-theme-wp-admin-related?replies=2) * Don’t do that, it really makes it hard for us to support you. If it weren’t for the fact that you’ve 2 moderators helping you I’d normally close the newer topic down with a note. * I’ll let it go this time. 😉 * > A succesful save with twentyeleven, so that’s my theme’s issue right? * It’s _probably_ is a theme issue but still could be something else. Have you updated anything lately? * Let’s see if it can be narrowed down some more. While the Twenty Eleven theme is active, deactivate all of your plugins and then switch back to that theme. * Did the error come back after all of the plugins were deactivated? * Thread Starter [carloravelli](https://wordpress.org/support/users/carloravelli/) * (@carloravelli) * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/#post-3154547) * Sorry, but getting no answer and not being able to find anything else in on the internet being similar to this gets stressful. I’ll stick to the rules from now on 🙂 * Only active plugin was Contact Form 7, did as you said and still the same issue. Regarding updates, only things I did were replace wp-admin and wp-includes (only those folders, not the config files and such) and upload and remove tinymce. * Moderator [Jan Dembowski](https://wordpress.org/support/users/jdembowski/) * (@jdembowski) * Forum Moderator and Brute Squad * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/#post-3154551) * Theme issue or `wp-config.php` but what’s changed…? * Which theme are you using? If you have backups (…you do have backups right…?) then save your current theme and see if uploading a fresh copy see if that can narrow it down even more. * Thread Starter [carloravelli](https://wordpress.org/support/users/carloravelli/) * (@carloravelli) * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/#post-3154554) * I’m using a custom theme made by me and 2 other front-end developers. Everything made from the ground up basically. * Back-ups are made when the website is ready to go live so nope… none yet. * I keep thinking it’s got to do with the metaboxes file, because I really didn’t make any other changes, certainly nothing to do with php. I did edit the admin- header.php file but then again I completely replaced wp-admin. * If you really need to I could post a link to the development url of the site, not sure if that would help. * Moderator [keesiemeijer](https://wordpress.org/support/users/keesiemeijer/) * (@keesiemeijer) * [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/#post-3154559) * > Warning: Cannot modify header information – headers already sent by (output > started at /home/yc/domains/yc.keytoe.nl/public_html/wp-content/themes/yourconnector/ > inc/metaboxes.php:6) in /home/yc/domains/yc.keytoe.nl/public_html/wp-includes/ > pluggable.php on line 881 * Is that the only error? Viewing 15 replies - 1 through 15 (of 19 total) 1 [2](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/page/2/?output_format=md&replies=12) [→](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/page/2/?output_format=md&replies=12) The topic ‘Cannot modify header information error – functions.php’ is closed to new replies. * In: [Fixing WordPress](https://wordpress.org/support/forum/how-to-and-troubleshooting/) * 19 replies * 5 participants * Last reply from: [keesiemeijer](https://wordpress.org/support/users/keesiemeijer/) * Last activity: [13 years, 7 months ago](https://wordpress.org/support/topic/cannot-modify-header-information-error-functionsphp/page/2/#post-3154563) * Status: resolved ## Topics ### Topics with no replies ### Non-support topics ### Resolved topics ### Unresolved topics ### All topics