Title: Cannot modify header but folder excluded
Last modified: January 26, 2023

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# Cannot modify header but folder excluded

 *  Resolved [Steven Jay Cohen](https://wordpress.org/support/users/stevenjaycohen/)
 * (@stevenjaycohen)
 * [3 years, 4 months ago](https://wordpress.org/support/topic/cannot-modify-header-but-folder-excluded/)
 * `PHP Warning: Cannot modify header information - headers already sent by (output
   started at /home3/xxx/public_html/website.com**/tracker/** index.php:1) in /home3/
   xxx/public_html/website.com/wp-content/plugins/wp-super- cache/wp-cache-phase2.
   php on line 1478`
 * **/tracker/** is already listed in Rejected URL Strings on its own line (it is
   not part of the wordpress install), using PHP v8.1
 * Any thoughts?

Viewing 2 replies - 1 through 2 (of 2 total)

 *  [Daniel](https://wordpress.org/support/users/ihenetudan/)
 * (@ihenetudan)
 * [3 years, 4 months ago](https://wordpress.org/support/topic/cannot-modify-header-but-folder-excluded/#post-16414961)
 * Hi [@stevenjaycohen](https://wordpress.org/support/users/stevenjaycohen/),
 * This has to do with the way WordPress loads files and scripts. In general, WordPress
   uses a bootstrap process to load its PHP files and scripts. So, even though **`/
   tracker/`** is not part of the WordPress install, it looks like it’s still interfering
   with the bootstrap process, likely because that `index.php` file is being used
   somewhere in a plugin or theme code.
 * There is a PHP `header` function call on [that referenced line (1478)](https://github.com/Automattic/wp-super-cache/blob/trunk/wp-cache-phase2.php#L1478)
   of the `wp-cache-phase2.php` file, which is why that PHP warning occurs. That
   warning error is caused by output being sent to the browser before the HTTP headers
   are set in the PHP script.
 * The error message is indicating that some extraneous output started at line 1
   of the `tracker/index.php` file. This could be caused by a number of things, 
   such as whitespace before an opening PHP tag or an echo or print statement that
   is executed before the headers are set.
 * To fix this error, you’ll need to locate the source of the output and remove 
   it or move it to a more appropriate location. I can’t give more specific advice
   without knowing what that `tracker/index.php` file does exactly.
 * I hope this helps.
 *  Plugin Support [Jay](https://wordpress.org/support/users/bluejay77/)
 * (@bluejay77)
 * [3 years, 4 months ago](https://wordpress.org/support/topic/cannot-modify-header-but-folder-excluded/#post-16441655)
 * Hi there,
 * It has been more than one week since we have heard from you, so I’m marking this
   topic as resolved.
 * But if you have any further questions or need some more help, you’re welcome 
   to reply here or open another thread.

Viewing 2 replies - 1 through 2 (of 2 total)

The topic ‘Cannot modify header but folder excluded’ is closed to new replies.

 * ![](https://ps.w.org/wp-super-cache/assets/icon-256x256.png?rev=3506220)
 * [WP Super Cache](https://wordpress.org/plugins/wp-super-cache/)
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 * 2 replies
 * 3 participants
 * Last reply from: [Jay](https://wordpress.org/support/users/bluejay77/)
 * Last activity: [3 years, 4 months ago](https://wordpress.org/support/topic/cannot-modify-header-but-folder-excluded/#post-16441655)
 * Status: resolved