PHP正則照合日

    /**
     *       xxxx-xx-xx  
     */
    public function regular()
    {
        $rules = '/^(\d{4}-\d{2}-\d{2})?$/';
        $pattern = '/^\d{4}-\d{2}-\d{2}$/'; //   
        $val = '2018-08-08';

        if(preg_match($rules,$val)){
            echo '  ';
        }else{
            echo '  ';
        }
    }