I am getting the following php error:

PHP Warning:  call_user_func_array() expects parameter 1 to be a valid callback, function '' not found or invalid function name in /home/example/public_html/wp-includes/class-wp-hook.php on line 286

The issue is that there is no function name mentioned, how can I identify which function is causing this error?

  • 1
    That error suggests that there's a call made to add_action() or add_filter() where the callback is an "empty" one - e.g. it's '' as in add_action( 'init', '' ) or maybe add_action( 'hook_name', $func ) where $func is empty (NULL, '', etc.). Query Monitor can help you identify the hook name and also the plugin/theme file, if it's caused by a code in a plugin or the active theme.
    – Sally CJ
    Commented Nov 20, 2019 at 11:25

1 Answer 1


There was a filter in the child theme causing the issue:


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