call_user_func_array() expects parameter 1 to be a valid callback, first array member is not a valid class name or object in C:\xampp\htdocs\Block Lands\signer\lib\DataSource.php on line 143 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.