I’m seeing the following message in the error log of one of my child sites:
PHP Warning: call_user_func_array() expects parameter 1 to be a valid callback, class ‘MainWP_Security’ not found in …l/wp-includes/class-wp-hook.php on line 287
I see that there is a recently closed discussion of this topic without a resolution. Perhaps we can figure it out this time.
This problem has been reported earlier, but since the previous poster has never opened a ticket and we haven’t been able to duplicate the problem on our setups, the system closed the topic after 30 days of inactivity. So let’s continue from here.
For the start, can you please send me some basic info about your child site: