wp-includes/class-wp-hook.php on line 298

This may be a plugin or theme conflict. Please attempt to disable all plugins, and use one of the default (Twenty*) themes. If the problem goes away, enable them one by one to identify the source of your troubles.

hi,have no access to admin part( i wrote),how to disable plugins and to change theme?

!!!Have no access to admin part of mysite
https://mysite/wp-admin/

getting error messages!!!

Warning: call_user_func_array() expects parameter 1 to be a valid callback, no array or string given in /home/mysite/public_html/wp-includes/class-wp-hook.php on line 298

Warning: Cannot modify header information – headers already sent by (output started at /home/mysite/public_html/wp-includes/class-wp-hook.php:298) in /home/mysite/public_html/wp-includes/pluggable.php on line 1179

See https://www.wpbeginner.com/plugins/how-to-deactivate-all-plugins-when-not-able-to-access-wp-admin/ to deactivate *all* plugins. Remember, this is just a quick test to see if the issue is with a plugin.

hi,thanks,resolved problem