php接口如何正确使用

<?phpnamespace Home\Tool;;use Home\Tool;/**
 * Created by PhpStorm.
 * User: smile
 * Date: 2018/1/4
 * Time: 20:36
 */interface game_interface{
    public static function caiji();
    public static function js();
    public static function save();
    public static function check_guize();
    public static function fanshui();}

<?phpnamespace Home\Tool;;use Home\Tool;/**
 * Created by PhpStorm.
 * User: smile
 * Date: 2018/1/4
 * Time: 20:36
 */abstract class Game implements game_interface{}

<?phpnamespace Home\Tool;use Home\Tool;class Pk10 extends Game {
    public static $name ="北京赛车";    public static function js()
    {
        // TODO: Implement js() method.
        caiji();
    }    public static function caiji()
    {
        // TODO: Implement caiji() method.
    }    public static function save()
    {
        // TODO: Implement save() method.
    }    public static function check_guize()
    {
        // TODO: Implement check_guize() method.
    }    public static function fanshui()
    {
        // TODO: Implement fanshui() method.
    }
}