protected function add_filter($key, $value, $allowmultiple = false) {
        if ($allowmultiple || empty($this->get_filter_values($key))) {
            $this->filtersapplied[] = [$key, $value];
        }
    }
protected function add_filter($key, $value, $allowmultiple = false) {
        if ($allowmultiple || empty($this->get_filter_values($key))) {
            $this->filtersapplied[] = [$key, $value];
        }
    }
protected function add_filter ( $ key , $ value , $ allowmultiple = false ) { if ( $ allowmultiple || empty ( $ this -> get_filter_values ( $ key ) ) ) { $ this -> filtersapplied [ ] = [ $ key , $ value ] ; } }
Adds an applied filter

@param mixed $key
@param mixed $value
@param bool $allowmultiple
Adds an applied filter