This is what the error log shows for each attempt at a search:
PHP Fatal error: Declaration of IPS\Theme\hook1::filters() must be compatible with IPS\Theme\class_core_front_search::filters($baseUrl, $count, $id, $action, $elements, $hiddenValues, $actionButtons, $uploadField, $class = '', $attributes = [], $sidebar = null, $form = null, $errorTabs = null) in /home/osforums/public_html/system/Theme/Theme.php(951) : eval()'d code on line 173