call_user_func_array() expects parameter 1 to be a valid callback, class 'WP_TEST' does not have a method 'wp_test_option' in /Applications/XAMPP/xamppfiles/htdocs/wordpress/wp-includes/class-wp-hook.php on line 287 code example

Example: Warning: call_user_func_array() expects parameter 1 to be a valid callback

Somewhere in your theme or plugins is a line like this:

add_filter( 'something', 'regis_options' );
Could also be add_action(). Find that piece of code and remove or fix it.