Fatal error: Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, function "wp_ob_end_flush_all" not found or invalid function name in /home/hamedyou/public_html/wp-includes/class-wp-hook.php:324 Stack trace: #0 /home/hamedyou/public_html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() #1 /home/hamedyou/public_html/wp-includes/plugin.php(517): WP_Hook->do_action() #2 /home/hamedyou/public_html/wp-includes/load.php(1270): do_action() #3 [internal function]: shutdown_action_hook() #4 {main} thrown in /home/hamedyou/public_html/wp-includes/class-wp-hook.php on line 324