$str = "中华人民共和国";        $len = mb_strlen($str,‘utf-8‘);        if($len>=6){            $str1 = mb_substr($str,0,2,‘utf-8‘);            $str2 = mb_substr($str,$len-2,2,‘utf-8‘);        }        else{            $str1 = mb_substr($str,0,1,‘utf-8‘);            $str2 = mb_substr($str,$len-1,1,‘utf-8‘);                    }        $this->assign(‘str1‘,$str1);        $this->assign(‘str2‘,$str2);        $this->assign(‘str‘,$str1.‘**‘.$str2);        $this->assign(‘strold‘,substr_replace($str,‘**‘,2,2));