Valid callback

Ahojte,

Potreboval by som vyriesit na mojej stranke problem nizsie.
Za kazdu radu dakujem

Warning: call_user_func_array() expects parameter 1 to be a valid callback, function ‚wp_ob_end_flush_all‘ not found or invalid function name in D:\WWW\wof_CSM\wp-includes\class-wp-hook.php on line 303
Call Stack
# Time Memory Function Location
1 1.6845 25270808 shutdown_action_hook( ) …\load.php:0
2 1.6845 25270808 do_action( ) …\load.php:1097
3 1.6845 25271080 WP_Hook->do_action( ) …\plugin.php:470
4 1.6845 25271080 WP_Hook->apply_filters( ) …\class-wp-hook.php:329