Title: Error Cannot modify header information
Last modified: November 24, 2019

---

# Error Cannot modify header information

 *  Resolved [logaritym](https://wordpress.org/support/users/logaritym/)
 * (@logaritym)
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/)
 * Hello. I tried to rename one of the custom posts and then the following error
   appeared on my website:
    Warning: Cannot modify header information – headers 
   already sent by (output started at /bla-bla-bla/wp-content/plugins/custom-post-
   type-ui/custom-post-type-ui.php:381) in /bla-bla-bla/ltdspace/wp-includes/functions.
   php on line 5946
 * If I deactivate the plugin, everything works fine. If I activate it, the error
   appears again. Any idea how to fix it? I tried to delete the plugin and install
   it again, but it didn’t help.

Viewing 15 replies - 1 through 15 (of 16 total)

1 [2](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/page/2/?output_format=md)
[→](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/page/2/?output_format=md)

 *  Plugin Contributor [Michael Beckwith](https://wordpress.org/support/users/tw2113/)
 * (@tw2113)
 * The BenchPresser
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/#post-12170237)
 * Honestly not sure what’s going on there. Line 381 from our plugin with version
   1.7.1 is linked to below and is just a foreach loop.
 * [https://github.com/WebDevStudios/custom-post-type-ui/blob/1.7.1/custom-post-type-ui.php#L381](https://github.com/WebDevStudios/custom-post-type-ui/blob/1.7.1/custom-post-type-ui.php#L381)
 * In terms of line 5946 from the WP core function, it’s a header() call
 * [https://github.com/WordPress/WordPress/blob/5.3/wp-includes/functions.php#L5946](https://github.com/WordPress/WordPress/blob/5.3/wp-includes/functions.php#L5946)
 * Basically somewhere in your install, something is invoking send_frame_options_header()
   and throwing things off. I sadly don’t have any sort of “do these things” solution
   for this case.
 *  [liamc](https://wordpress.org/support/users/liamc/)
 * (@liamc)
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/#post-12183232)
 * Hello Michael, i Have the same Problem and i dont understand whats causing it.
   I Also tried to reinstall the Plugin but it still did not work either 🙁
 * Could it be something with the newest WP version?
 * Kind Regards, Liam
 *  [liamc](https://wordpress.org/support/users/liamc/)
 * (@liamc)
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/#post-12183269)
 * Also i am using ACF Costum fields and there are some similar problems there to…
   maybe the problem is somehow connected i dont know much about coding:/ So maybe
   the Guys from WeDevs have noticed something.
    -  This reply was modified 6 years, 6 months ago by [liamc](https://wordpress.org/support/users/liamc/).
 *  Plugin Contributor [Michael Beckwith](https://wordpress.org/support/users/tw2113/)
 * (@tw2113)
 * The BenchPresser
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/#post-12183437)
 * No known conflicts on our end for the latest WP and the latest CPTUI.
 * Is it the exact same error at `/wp-includes/functions.php on line 5946` that 
   you’re seeing? or is it a different location possibly? Same question for the 
   CPTUI line at `/wp-content/plugins/custom-post-type-ui/custom-post-type-ui.php
   line 381`
 * Closest i can find is that the function that that header() line is from is called
   on these two:
 * wp-includes/default-filters.php
    316:add_action( ‘login_init’, ‘send_frame_options_header’,
   10, 0 ); 357:add_action( ‘admin_init’, ‘send_frame_options_header’, 10, 0 );
 * For what it’s worth, re-installing won’t affect anything here, as the issue is
   coming up during init hook runs.
 *  [liamc](https://wordpress.org/support/users/liamc/)
 * (@liamc)
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/#post-12184172)
 * Hello Michael Thx for the fast reply:)
 * I get the same error on line 381, but the other error has a different line, but
   seems to be the same.
 * Here is the error getting displayed (i know php error logs tent to be not usefull
   for support, but maybe this one is):
 * Warning: strlen) expects parameter 1 to be string, object
    given in /homepages/
   36/bla-bla-bla bla-bla/htdocs/WastedSociety/wp- includes/formatting.php on line
   3380
 * Warning: strlen) expects parameter 1 to be string, object
    given in /homepages/
   bla/bla-bla-bla/htdocs/WastedSociety/wp- includes/formatting.php on line 3380
 * Warning: strlen) expects parameter 1 to be string, object
    given in homepages/
   bla/bla-bla-bla/htdocs/WastedSociety/wp includes/formatting.php on line 3380
 * (i have censored some server related information)
 * Iam very bad with PhP and Javascript, so for me it is very difficult to find 
   the issue, but it seems that there is something wrong with cpt ui or something
   new, that we have to care about when creating those post types. Maybe under certain
   circumstances, the php crashes due CPT UI. The error occured, after i set up 
   a new post type after updating my wp version. After the error occured, i deleted
   the new post type, but the error was still existing. I firtst thaught it would
   something else, but after i logged out, i could not login to my backend again,
   because of this error. I had to temporarly deinstall the plugin, because the 
   error blocked me from loggin in with wp-admin. So i had to delete the plugin 
   with FTP. Hope you find something out, i dont want to use costum post type over
   a theme, because im scared, to loose those post types, when a update for the 
   theme is out.
 * Kind regards and sorry for the long text
    Liam
    -  This reply was modified 6 years, 6 months ago by [liamc](https://wordpress.org/support/users/liamc/).
 *  [liamc](https://wordpress.org/support/users/liamc/)
 * (@liamc)
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/#post-12185751)
 * Sorry, i dont know if the previous message went thru so im sending it again:
 * Hello Michael Thx for the fast reply:)
 * I get the same error on line 381, but the other error has a different line, but
   seems to be the same.
 * Here is the error getting displayed (i know php error logs tent to be not usefull
   for support, but maybe this one is):
 * Warning: strlen) expects parameter 1 to be string, object
    given in /homepages/
   36/bla-bla-bla bla-bla/htdocs/WastedSociety/wp- includes/formatting.php on line
   3380
 * Warning: strlen) expects parameter 1 to be string, object
    given in /homepages/
   bla/bla-bla-bla/htdocs/WastedSociety/wp- includes/formatting.php on line 3380
 * Warning: strlen) expects parameter 1 to be string, object
    given in homepages/
   bla/bla-bla-bla/htdocs/WastedSociety/wp includes/formatting.php on line 3380
 * (i have censored some server related information)
 * Iam very bad with PhP and Javascript, so for me it is very difficult to find 
   the issue, but it seems that there is something wrong with cpt ui or something
   new, that we have to care about when creating those post types. Maybe under certain
   circumstances, the php crashes due CPT UI. The error occured, after i set up 
   a new post type after updating my wp version. After the error occured, i deleted
   the new post type, but the error was still existing. I firtst thaught it would
   something else, but after i logged out, i could not login to my backend again,
   because of this error. I had to temporarly deinstall the plugin, because the 
   error blocked me from loggin in with wp-admin. So i had to delete the plugin 
   with FTP. Hope you find something out, i dont want to use costum post type over
   a theme, because im scared, to loose those post types, when a update for the 
   theme is out.
 * Kind regards and sorry for the long text
    Liam
 *  Plugin Contributor [Michael Beckwith](https://wordpress.org/support/users/tw2113/)
 * (@tw2113)
 * The BenchPresser
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/#post-12186497)
 * Nothing in the provided error logs is able to help me at all Line 3380 in formatting.
   php is a line inside an `is_email()` check and we don’t utilize that function
   at all.
 * That said, even still, there’s nothing I can see that I could consider changing
   here. It’s a case of 2 people reporting a similar issue out of thus far our entire
   userbase. I definitely want to help, but I need leads and the ability to reproduce
   on my own. As is, the only thing I have is that two different things are being
   run on the `init` hook.
 * Can you use the Tools > Debug Info tab to get me a copy of the debug info. Something
   may present itself there or at least I could see about any plugins that look 
   like they could be contributing as well.
 *  [liamc](https://wordpress.org/support/users/liamc/)
 * (@liamc)
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/#post-12186994)
 * Hello Micheal Thanks for the reply and the:)
    I have now reinstalled cpt ui and
   deleted all my Post types. the error is gone, but comes back as soon as i create
   a Post type. I Have tried to change my theme and the latest installed Plugins,
   but it does not help:/ Maybe you could tell me, what usually could cause such
   a problem with the init hook.
 * Here would be the Debug mode:
 * Notice: (Neve Pro Addon: 1.1.2/Orbit Fox Companion: 2.8.13 was deactivated after
   this was copied)
 *  ### Begin Custom Post Type UI Debug Info ###
 *  Multisite: No
 *  SITE_URL: [https://wastedsociety.ch](https://wastedsociety.ch)
    HOME_URL: [https://wastedsociety.ch](https://wastedsociety.ch)
 *  WordPress Version: 5.3
    Permalink Structure: /%postname%/ Active Theme: Astra
   2.1.3
 *  Registered Post Types: post, page, attachment, revision, nav_menu_item, custom_css,
   customize_changeset, oembed_cache, user_request, wp_block, elementor_library,
   acf-field-group, acf-field, wpcf7_contact_form, dj_portfolios, dj_service, pafe-
   form-database, wppb-roles-editor, wpuf_profile, wpuf_coupon, wpuf_subscription,
   wpuf_forms, wpuf_input, jet-engine-booking, jet-engine, elementor_font, elementor_icons
 *  PHP Version: 7.3.12
    MySQL Version: 5.7.27 Web Server Info: Apache
 *  Show On Front: page
    Page On Front: Wastedsociety (#91) Page For Posts: Edit
   Profile 1 (#0)
 *  WordPress Memory Limit: 40MB
 *  TOTAL PLUGINS: 29
 *  ACTIVE PLUGINS: (27)
 *  Advanced Custom Fields PRO: 5.8.7
    Akismet Anti-Spam: 4.1.3 Asset CleanUp Pro:
   Page Speed Booster: 1.1.5.2 CM Custom Reports Pro: 1.2.0 Contact Form 7: 5.1.5
   Custom Post Type UI: 1.7.1 Elementor: 2.7.5 Elementor Pro: 2.7.3 Element Pack:
   4.1.0 Happy Elementor Addons: 2.3.0 Happy Elementor Addons Pro: 1.0.0 iframe:
   4.4 Imagify: 1.9.8.1 JetBooking: 1.0.2 JetElements For Elementor: 2.1.5 JetEngine:
   2.1.4 JetTricks: 1.2.3 Orbit Fox Companion: 2.8.13 Piotnet Addons For Elementor:
   2.2.0 Piotnet Addons For Elementor Pro: 5.15.11 Profile Builder – Custom CSS 
   Classes on fields: 1.0.4 Profile Builder – Customization Toolbox Add-On: 1.0.8
   Profile Builder – List user meta with a shortcode: 1.2 Profile Builder Pro: 3.0.6
   UpdraftPlus – Backup/Restore: 1.16.20 WP User Frontend: 3.1.13 WP User Frontend
   Pro – business: 3.1.11
 *  INACTIVE PLUGINS: (2)
 *  Neve Pro Addon: 1.1.2
    WP Rocket: 3.4.2.2
 *  Post Types:
    {“dj_portfolios”:{“name”:”dj_portfolios”,”label”:”Dj Portfolios”,”
   singular_label”:”Dj Portfolio”,”description”:””,”public”:”true”,”publicly_queryable”:”
   true”,”show_ui”:”true”,”show_in_nav_menus”:”true”,”delete_with_user”:”false”,”
   show_in_rest”:”true”,”rest_base”:””,”rest_controller_class”:””,”has_archive”:”
   false”,”has_archive_string”:””,”exclude_from_search”:”false”,”capability_type”:”
   post”,”hierarchical”:”false”,”rewrite”:”true”,”rewrite_slug”:””,”rewrite_withfront”:”
   true”,”query_var”:”true”,”query_var_slug”:””,”menu_position”:””,”show_in_menu”:”
   true”,”show_in_menu_string”:””,”menu_icon”:””,”supports”:[“title”,”editor”,”thumbnail”,”
   excerpt”,”trackbacks”,”custom-fields”,”comments”,”revisions”,”author”,”page-attributes”,”
   post-formats”],”taxonomies”:[],”labels”:{“menu_name”:”Dj Portfolios”,”all_items”:”
   All Dj Portfolios”,”add_new”:”Add new”,”add_new_item”:”Add new Dj Portfolio”,”
   edit_item”:”Edit Dj Portfolio”,”new_item”:”New Dj Portfolio”,”view_item”:”View
   Dj Portfolio”,”view_items”:”View Dj Portfolios”,”search_items”:”Search Dj Portfolios”,”
   not_found”:”No Dj Portfolios found”,”not_found_in_trash”:”No Dj Portfolios found
   in trash”,”parent”:”Parent Dj Portfolio:”,”featured_image”:”Featured image for
   this Dj Portfolio”,”set_featured_image”:”Set featured image for this Dj Portfolio”,”
   remove_featured_image”:”Remove featured image for this Dj Portfolio”,”use_featured_image”:”
   Use as featured image for this Dj Portfolio”,”archives”:”Dj Portfolio archives”,”
   insert_into_item”:”Insert into Dj Portfolio”,”uploaded_to_this_item”:”Upload 
   to this Dj Portfolio”,”filter_items_list”:”Filter Dj Portfolios list”,”items_list_navigation”:”
   Dj Portfolios list navigation”,”items_list”:”Dj Portfolios list”,”attributes”:”
   Dj Portfolios attributes”,”name_admin_bar”:”Dj Portfolio”,”item_published”:”Dj
   Portfolio published”,”item_published_privately”:”Dj Portfolio published privately.”,”
   item_reverted_to_draft”:”Dj Portfolio reverted to draft.”,”item_scheduled”:”Dj
   Portfolio scheduled”,”item_updated”:”Dj Portfolio updated.”,”parent_item_colon”:”
   Parent Dj Portfolio:”},”custom_supports”:””},”dj_service”:{“name”:”dj_service”,”
   label”:”Dj Services”,”singular_label”:”Dj Service”,”description”:””,”public”:”
   true”,”publicly_queryable”:”true”,”show_ui”:”true”,”show_in_nav_menus”:”true”,”
   delete_with_user”:”false”,”show_in_rest”:”true”,”rest_base”:””,”rest_controller_class”:””,”
   has_archive”:”false”,”has_archive_string”:””,”exclude_from_search”:”false”,”capability_type”:”
   post”,”hierarchical”:”false”,”rewrite”:”true”,”rewrite_slug”:””,”rewrite_withfront”:”
   true”,”query_var”:”true”,”query_var_slug”:””,”menu_position”:””,”show_in_menu”:”
   true”,”show_in_menu_string”:””,”menu_icon”:””,”supports”:[“title”,”editor”,”thumbnail”,”
   excerpt”,”trackbacks”,”custom-fields”,”comments”,”revisions”,”author”,”page-attributes”,”
   post-formats”],”taxonomies”:[],”labels”:null,”custom_supports”:””}}
 *  Taxonomies:
    []
 *  ### End Debug Info ###
 *  Plugin Contributor [Michael Beckwith](https://wordpress.org/support/users/tw2113/)
 * (@tw2113)
 * The BenchPresser
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/#post-12187054)
 * Will see what I can deduce with this, if anything.
 * What confuses me the most is that at line 381 in our plugin, we don’t send any
   output.
 *  Plugin Contributor [Michael Beckwith](https://wordpress.org/support/users/tw2113/)
 * (@tw2113)
 * The BenchPresser
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/#post-12187056)
 * If you haven’t yet, and are able, could you try deactivating other plugins to
   see if it goes away during that time? I’m not seeing a lot of plugins that I 
   recognize and may not be publicly available for me to check out.
 * If you find it does go away after deactivating a different plugin than CPTUI,
   but then comes back once that one is re-activated, we probably have our culprit
   for conflict of some sort.
 *  Plugin Contributor [Michael Beckwith](https://wordpress.org/support/users/tw2113/)
 * (@tw2113)
 * The BenchPresser
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/#post-12190008)
 * Still not managing to recreate at all myself.
 * I am legit curious if there’s any crossover/sharing of active plugins between
   [@liamc](https://wordpress.org/support/users/liamc/) and [@logaritym](https://wordpress.org/support/users/logaritym/)
 *  [liamc](https://wordpress.org/support/users/liamc/)
 * (@liamc)
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/#post-12190329)
 * Hello Michael, Thank you a lot:)
    It is the WPUser Frontend Plugin, wich was 
   causing this errors :/ After deactivating WP user frontend, creating post types
   was no problem anymore. But the WP User frontend PLugin is also from WeDevs, 
   so i think they should be compatible… I Would really need the WP User frontend
   togheter with the CPT UI.
 * You May check this one out it is a new topic running in the WP User frontend 
   Support section:
    [https://wordpress.org/support/topic/strlen-expects-parameter/#post-12184062](https://wordpress.org/support/topic/strlen-expects-parameter/#post-12184062)
 * Maybe it is connected to the same Problem. I Will link this topic in the Support
   topic mentioned above.
 * Kind Regards
    Liam
 *  Plugin Contributor [Michael Beckwith](https://wordpress.org/support/users/tw2113/)
 * (@tw2113)
 * The BenchPresser
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/#post-12190661)
 * For what it’s worth, it’s likely not a case of anything that one plugin is doing
   that is directly “targeted” or “conflicted” with the other one.
 * It’s likely more they’re both trying to do their own thing and some results from
   one is happening to cause issues with the other.
 * That said, I could believe some general errors being output to the browser, like
   that strlen error, causing header issues like experienced here. If they can provide
   information about what they changed to fix the issue, I could technically help
   you patch it up on your own.
 * I’ve done some extra digging, and I would bet money on this change being the 
   fix needing made:
 * [https://github.com/weDevsOfficial/wp-user-frontend/commit/15717355874c01d492c372822533d55c9870adb9](https://github.com/weDevsOfficial/wp-user-frontend/commit/15717355874c01d492c372822533d55c9870adb9)
 * Specifically the `is_string( $id_or_email )` part being added.
 * It is a change on their side rather than ours, but I’m confident here. Chances
   are it’ll remove the strlen errors above and thus stop the headers from being
   sent early, and everything working together.
 *  [liamc](https://wordpress.org/support/users/liamc/)
 * (@liamc)
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/#post-12191493)
 * hello Michael thank you very much!
    This fixed another problem i had within Pages
   🙂
 * But the fatal error still comes up as soon as i create a new post type or update
   one. I Found a workaround. if i simply deactivate WP User frontend before creating
   or updating CPTs with CPT UI, the error does not accure, even when reactivating
   WP User frontend afterwards. So i could life with that, simply need to pay attention
   to first deactivating WP User Frontend, before doing any Updates.
 * But what confuses me a bit is, that i did no costum changes tho the wordpress
   code or themes etc. The only Plugins wich, in my beliefe, could change some background
   code are Profile Builder, Wp User frontend, Costum CPT UI, Asset Cleanup , AFC
   and Piotnet Elements.
 * If i understand this right there must be a wrong setting inside a certain plugin
   wich would cause that? I Jus thinked about a Bug within WP User frontend, because
   i used all of those other Plugins mentioned above befor installing WP User frontend
   and CPT UI and it also worked. But im Really not an expert.
 * Im am so Glad you took the time to help me. Thank you very much i now have a 
   workaround and im back in business 😀
 *  Plugin Contributor [Michael Beckwith](https://wordpress.org/support/users/tw2113/)
 * (@tw2113)
 * The BenchPresser
 * [6 years, 6 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/#post-12192302)
 * 1) Realistically unless you’re in active development or adding custom content
   types regularly, you shouldn’t have need to deactivate/reactivate things here.
 * 2) “Headers already sent” errors pretty much mean *something* was sent to the
   browser, even something as simple as white space or in this case, probably an
   error message originating from somewhere, before the rest of things can get finished
   doing their thing, thus causing this error once they try to. Code that needed
   to run and do things before the output started.
 * If you have error reporting turned on that would cause error logging to show 
   through to the browser, that’s probably contributing factor, and getting those
   hidden from general viewing would alleviate the issue too.

Viewing 15 replies - 1 through 15 (of 16 total)

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

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 * [Custom Post Type UI](https://wordpress.org/plugins/custom-post-type-ui/)
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 * 16 replies
 * 3 participants
 * Last reply from: [Michael Beckwith](https://wordpress.org/support/users/tw2113/)
 * Last activity: [6 years, 5 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-information-15/page/2/#post-12210677)
 * Status: resolved