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[Resolved] Warning: Cannot modify header information - headers already sent by

This thread is resolved. Here is a description of the problem and solution.

Problem:
The client is encountering a 'Cannot modify header information' error in both the admin pages and the Elementor editor of their WordPress site. This issue is related to the WPML plugin and appears to be triggered by specific conditions linked to the client's user account.
Solution:
1. We recommend creating a new admin user and deleting the old one to see if this resolves the issue.
2. If the problem persists, consider lowering the PHP version to 8.0 as the current version might be causing compatibility issues with WPML and WordPress.
3. Ensure that the display of errors and warnings is disabled, which is advisable for production sites unless debugging.

If these steps do not resolve the issue or if the solution seems outdated or irrelevant to your case, please visit our known issues page and check for any related updates. We also recommend confirming that you have the latest versions of themes and plugins installed. If the problem continues, do not hesitate to open a new support ticket.

This is the technical support forum for WPML - the multilingual WordPress plugin.

Everyone can read, but only WPML clients can post here. WPML team is replying on the forum 6 days per week, 22 hours per day.

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This topic contains 17 replies, has 0 voices.

Last updated by Dražen 2 weeks, 1 day ago.

Assisted by: Dražen.

Author Posts
July 24, 2025 at 5:48 am #17265949

Dražen
Supporter

Languages: English (English )

Timezone: Europe/Zagreb (GMT+02:00)

Hello,

thanks for getting back.

1) You can try creating a new admin user and delete that one, and continue using that new one, if that helps. If not, you can share your admin account and I can check further.

2) These are just some depracted and warning message, not errors. You are using latest PHP which might give such warning, while WP / WPML still provide full support for latest PHP.Please try to lower PHP to 8.0.

Regards,
Drazen
July 24, 2025 at 9:48 am #17266777

Enis

Hello Drazen,

In the wp-config file I had the below codes:

define( 'WP_DEBUG', false );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', true );
@ini_set( 'display_errors', 1 );

I turned error display off and not to print these warnings on screen. If you say these are not errors..

Do you think this would be enough as a solution ?
If you think that is not a solid solution I can share the admin user account with you.

Thanks
July 25, 2025 at 5:45 am #17269906

Dražen
Supporter

Languages: English (English )

Timezone: Europe/Zagreb (GMT+02:00)

Hello,

you have set to not display any errors or warning, which is okay and recommended for production website and if not debugging an issue.

It depends on you, if it is not causing any issue for you then it is okay, and since it is only happening for your user, it is mostly likely related to some info from your user account, but everything else should work fine.

Regards,
Drazen