How to solve the problem of WordPress "call_user_func_array() expectations" Recently, I upgraded to WordPress5.8, and everything was successfully completed. The error prompt "call_user_func_array() expects parameter 1 to be a valid callback" appeared on the background page. Fortunately, the foreground page can open normally Like( one ) 2021-08-22 WordPress Guide call_user_func_array() expects WordPress error Reading (1622)