Title: PHP error: Cannot modify header information Last modified: January 21, 2025 --- # PHP error: Cannot modify header information * [Dominique DC](https://wordpress.org/support/users/dominique_delcourt_com/) * (@dominique_delcourt_com) * [1 year, 2 months ago](https://wordpress.org/support/topic/php-error-cannot-modify-header-information-2/) * Hi, I have the following PHP Error in the server logs which repeats itself so many times :[21-Jan-2025 06:56:45 UTC] PHP Warning: Cannot modify header information– headers already sent in …/wp-content/plugins/sg-cachepress/core/File_Cacher/Cache. php on line 145Which comes from this line of code : * ```wp-block-code // Bail if the page is excluded from the cache. if ( ! $this->is_cacheable() ) { header( 'SG-F-Cache: BYPASS' ); return; } ``` * I have tried to flush the buffer, but I get the same result : * ```wp-block-code // Bail if the page is excluded from the cache. if ( ! $this->is_cacheable() ) { flush(); // Flush the buffer ob_flush(); header( 'SG-F-Cache: BYPASS' ); return; } ``` * `Thanks for your help !Kind regards,Dominique * The page I need help with: _[[log in](https://login.wordpress.org/?redirect_to=https%3A%2F%2Fwordpress.org%2Fsupport%2Ftopic%2Fphp-error-cannot-modify-header-information-2%2F%3Foutput_format%3Dmd&locale=en_US) to see the link]_ Viewing 3 replies - 1 through 3 (of 3 total) * Plugin Support [Svetoslav Vasev](https://wordpress.org/support/users/svetoslavvasev/) * (@svetoslavvasev) * [1 year, 2 months ago](https://wordpress.org/support/topic/php-error-cannot-modify-header-information-2/#post-18255915) * Hello [@dominique_delcourt_com](https://wordpress.org/support/users/dominique_delcourt_com/), * The warning you’ve encountered – Cannot modify header information – can be suppressed in most cases by setting the value of the PHP variable output_buffering to 1. * If you are a SiteGround customer, please contact us by posting a ticket request and we will assist you further in case the warning persists after enabling the PHP output buffering. * Kind Regards, * Svetoslav Vasev * Thread Starter [Dominique DC](https://wordpress.org/support/users/dominique_delcourt_com/) * (@dominique_delcourt_com) * [1 year, 2 months ago](https://wordpress.org/support/topic/php-error-cannot-modify-header-information-2/#post-18261939) * Dear Svetoslav Vasev, It is for one of my clients… the website is not hosted by SiteGround.I have tried with : **output_buffering = on**. but I get the exact same result.I had a very good speed page on my biggest article.. I would like to continue to use your plugin !Any other idea ? Kind regards,Dominique * `[23-Jan-2025 18:10:01 UTC] PHP Warning: Cannot modify header information - headers already sent in /srv/data/web/vhosts/phytopyo.alphanosos.com/htdocs/wp- content/plugins/sg-cachepress/core/File_Cacher/Cache.php on line 156 [23-Jan- 2025 18:12:01 UTC] PHP Warning: Cannot modify header information - headers already sent in /srv/data/web/vhosts/phytopyo.alphanosos.com/htdocs/wp-content/plugins/ sg-cachepress/core/File_Cacher/Cache.php on line 156 [23-Jan-2025 18:14:23 UTC] PHP Warning: Cannot modify header information - headers already sent in /srv/ data/web/vhosts/phytopyo.alphanosos.com/htdocs/wp-content/plugins/sg-cachepress/ core/File_Cacher/Cache.php on line 156 [23-Jan-2025 18:15:58 UTC] PHP Warning: Cannot modify header information - headers already sent in /srv/data/web/vhosts/ phytopyo.alphanosos.com/htdocs/wp-content/plugins/sg-cachepress/core/File_Cacher/ Cache.php on line 156 [23-Jan-2025 18:18:10 UTC] PHP Warning: Cannot modify header information - headers already sent in /srv/data/web/vhosts/phytopyo.alphanosos. com/htdocs/wp-content/plugins/sg-cachepress/core/File_Cacher/Cache.php on line 156 [23-Jan-2025 18:18:44 UTC] PHP Warning: Cannot modify header information - headers already sent in /srv/data/web/vhosts/phytopyo.alphanosos.com/htdocs/wp- content/plugins/sg-cachepress/core/File_Cacher/Cache.php on line 156 [23-Jan- 2025 18:20:57 UTC] PHP Warning: Cannot modify header information - headers already sent in /srv/data/web/vhosts/phytopyo.alphanosos.com/htdocs/wp-content/plugins/ sg-cachepress/core/File_Cacher/Cache.php on line 156 [23-Jan-2025 18:22:56 UTC] PHP Warning: Cannot modify header information - headers already sent in /srv/ data/web/vhosts/phytopyo.alphanosos.com/htdocs/wp-content/plugins/sg-cachepress/ core/File_Cacher/Cache.php on line 156 [23-Jan-2025 18:24:56 UTC] PHP Warning: Cannot modify header information - headers already sent in /srv/data/web/vhosts/ phytopyo.alphanosos.com/htdocs/wp-content/plugins/sg-cachepress/core/File_Cacher/ Cache.php on line 156 [23-Jan-2025 18:26:56 UTC] PHP Warning: Cannot modify header information - headers already sent in /srv/data/web/vhosts/phytopyo.alphanosos. com/htdocs/wp-content/plugins/sg-cachepress/core/File_Cacher/Cache.php on line 156[23-Jan-2025 18:32:03 UTC] PHP Warning: Cannot modify header information - headers already sent in /srv/data/web/vhosts/phytopyo.alphanosos.com/htdocs/wp- content/plugins/sg-cachepress/core/File_Cacher/Cache.php on line 156 [23-Jan- 2025 18:32:21 UTC] PHP Warning: Cannot modify header information - headers already sent in /srv/data/web/vhosts/phytopyo.alphanosos.com/htdocs/wp-content/plugins/ sg-cachepress/core/File_Cacher/Cache.php on line 156 * Plugin Support [Vladimir Trandev](https://wordpress.org/support/users/vtrandev/) * (@vtrandev) * [1 year, 2 months ago](https://wordpress.org/support/topic/php-error-cannot-modify-header-information-2/#post-18262223) * Hello [@dominique_delcourt_com](https://wordpress.org/support/users/dominique_delcourt_com/), * The PHP warning might be generated by another plugin’s script execution. Since we can not further check the case on our end, I would recommend you to disable all your plugins one by one in order to determine the exact plugin. * Have in mind that the mentioned warning is not a fatal PHP error and it can be safely disregarded. * Regards, * Vladimir Viewing 3 replies - 1 through 3 (of 3 total) The topic ‘PHP error: Cannot modify header information’ is closed to new replies. * ![](https://ps.w.org/sg-cachepress/assets/icon-256x256.gif?rev=2971889) * [Speed Optimizer - The All-In-One Performance-Boosting Plugin](https://wordpress.org/plugins/sg-cachepress/) * [Support Threads](https://wordpress.org/support/plugin/sg-cachepress/) * [Active Topics](https://wordpress.org/support/plugin/sg-cachepress/active/) * [Unresolved Topics](https://wordpress.org/support/plugin/sg-cachepress/unresolved/) * [Reviews](https://wordpress.org/support/plugin/sg-cachepress/reviews/) ## Tags * [Cannot modify header information](https://wordpress.org/support/topic-tag/cannot-modify-header-information/) * 3 replies * 3 participants * Last reply from: [Vladimir Trandev](https://wordpress.org/support/users/vtrandev/) * Last activity: [1 year, 2 months ago](https://wordpress.org/support/topic/php-error-cannot-modify-header-information-2/#post-18262223) * Status: not resolved