Using $this when not in object context错误信息

    public static function editPlaceSelect($places=[], $city_id=-1){
        if(is_array($places) && count($places)>0){
            foreach ($places as $place){
                $this->areaPlace($city_id, $place['area_id'], $place['address']);
            }
        }else{
            echo        '<li>';
            echo             '<select name="row_area_id" class="w-200 row_area_id">';
            echo                   '<option value="">-暂未开放-</option>';
            echo              '</select>';
            echo                   '<input type="text" name="row_area_address" class="w-300">';
            echo              '</li>';
        }
    }
    
    public static function areaPlace($city_id, $area_id, $address){
        echo        '<li>';
        echo             '<select name="row_area_id" class="w-200 row_area_id">';
        $this->areaSelect($city_id, $area_id);
        echo              '</select>';
        echo                   '<input type="text" name="row_area_address" class="w-300" value="'.$address.'">';
        echo              '</li>';
    }

self::areaPlace($city_id, $place['area_id'], $place['address'])；

$this->areaSelect($city_id, $area_id);