Title: PHP Warning: Cannot modify header information
Last modified: January 2, 2020

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# PHP Warning: Cannot modify header information

 *  Resolved [krazykatz911](https://wordpress.org/support/users/krazykatz911/)
 * (@krazykatz911)
 * [6 years, 5 months ago](https://wordpress.org/support/topic/php-warning-cannot-modify-header-information-11/)
 * I keep getting a ton of these errors. Please help:
 * `PHP Warning: Cannot modify header information - headers already sent by (output
   started at /home/site/public_html/wp-cron.php:28) in /home/site/public_html/wp-
   includes/functions.php on line 6029`
 * Thank you

Viewing 6 replies - 1 through 6 (of 6 total)

 *  Moderator [t-p](https://wordpress.org/support/users/t-p/)
 * (@t-p)
 * [6 years, 5 months ago](https://wordpress.org/support/topic/php-warning-cannot-modify-header-information-11/#post-12287298)
 * Try reviewing this info to solve header already sent problem: [https://wordpress.org/support/article/faq-troubleshooting/#how-do-i-solve-the-headers-already-sent-warning-problem](https://wordpress.org/support/article/faq-troubleshooting/#how-do-i-solve-the-headers-already-sent-warning-problem)
 *  Thread Starter [krazykatz911](https://wordpress.org/support/users/krazykatz911/)
 * (@krazykatz911)
 * [6 years, 5 months ago](https://wordpress.org/support/topic/php-warning-cannot-modify-header-information-11/#post-12287349)
 * Line 28 in wp-cron is
 * `fastcgi_finish_request();`
 * I checked and didn’t see any whitespace, or anything obvious.
 *  Moderator [t-p](https://wordpress.org/support/users/t-p/)
 * (@t-p)
 * [6 years, 5 months ago](https://wordpress.org/support/topic/php-warning-cannot-modify-header-information-11/#post-12287367)
 * To rule out any plugin/theme conflict try:
 * – [manually resetting your plugins](https://wordpress.org/support/article/faq-troubleshooting/#how-to-deactivate-all-plugins-when-not-able-to-access-the-administrative-menus)(
   no Dashboard access required). If that resolves the issue, reactivate each one
   individually until you find the cause.
 * – If that does not resolve the issue, access your server via [SFTP or FTP](https://wordpress.org/support/article/ftp-clients/),
   or a file manager in your hosting account’s control panel, navigate to `/wp-content/
   themes/` and rename the directory of your currently active theme. This will force
   the default theme to activate and hopefully rule-out a theme-specific issue (
   theme functions can interfere like plugins).
 *  Thread Starter [krazykatz911](https://wordpress.org/support/users/krazykatz911/)
 * (@krazykatz911)
 * [6 years, 5 months ago](https://wordpress.org/support/topic/php-warning-cannot-modify-header-information-11/#post-12287778)
 * I am working on that suggestion now. Will let ya know. Thank you.
 *  Thread Starter [krazykatz911](https://wordpress.org/support/users/krazykatz911/)
 * (@krazykatz911)
 * [6 years, 5 months ago](https://wordpress.org/support/topic/php-warning-cannot-modify-header-information-11/#post-12287990)
 * You were right. It was All In One WP Security & Firewall plugin causing the issue.
 *  Moderator [t-p](https://wordpress.org/support/users/t-p/)
 * (@t-p)
 * [6 years, 5 months ago](https://wordpress.org/support/topic/php-warning-cannot-modify-header-information-11/#post-12288041)
 * Glad its’ sorted 🙂

Viewing 6 replies - 1 through 6 (of 6 total)

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## Tags

 * [header](https://wordpress.org/support/topic-tag/header/)
 * [Modify](https://wordpress.org/support/topic-tag/modify/)
 * [php](https://wordpress.org/support/topic-tag/php/)
 * [warning](https://wordpress.org/support/topic-tag/warning/)

 * In: [Fixing WordPress](https://wordpress.org/support/forum/how-to-and-troubleshooting/)
 * 6 replies
 * 2 participants
 * Last reply from: [t-p](https://wordpress.org/support/users/t-p/)
 * Last activity: [6 years, 5 months ago](https://wordpress.org/support/topic/php-warning-cannot-modify-header-information-11/#post-12288041)
 * Status: resolved

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