Getting Warning: Cannot modify header information ..\wp-includes\pluggable.php on line 1223

[abahalkar]

Hello Team,

I have upgraded my WordPress from 4.8 to 5.0. while updating I am getting the warning

"Warning: Cannot modify header information - headers already sent by (output started at C:\wamp64\www\valud\current\speed_improve\wp-includes\script-loader.php:2338) in C:\wamp64\www\valud\current\speed_improve\wp-includes\pluggable.php on line 1223"

I tried and reinstalled WordPress multiple times but even thought maybe some bug will fix in upcoming version but still getting the issue in 5.0.2

please find attachment for more reference.

​http://nimb.ws/32qPyW

Thanks
Aniket

[faisal03]

Please try adding the following line in wp-config.php file

define(‘WP_DEBUG’, false);

[abahalkar]

Replying to faisal03:

Please try adding the following line in wp-config.php file

define(‘WP_DEBUG’, false);

Hi Faisal,

Thanks for replying. I know by this, I can hide warning and errors but this is my development setup. My purpose to submit a ticket is if any bug is in the new version that can be identified and should be fixed.

Thanks once again.

[mukesh27]

Hi @abahalkar, welcome to WordPres Trac! Thanks for the report.

Does the issue still happen with all plugins disabled and a default theme (Twenty Nineteen) activated?

Could you provide the steps to reproduce the issue on a clean install?

[SergeyBiryukov]

It looks like some plugin or theme calls print_admin_styles() too early.

[johnjamesjacoby]

Agree with @SergeyBiryukov this is the most likely cause.

Resolving as works-for-me.