php中用逗号分拆的字符串数组

function add_arrstr($arrstr,$oldarrstr){
        $arr=explode(',',$arrstr);
        $oldarr=explode(',',$oldarrstr);
        $newarr=array_unique(array_merge($arr, $oldarr));
        return  implode(",",$newarr);
}

function remove_arrstr($arrstr,$oldarrstr){
        $arr=explode(',',$arrstr);
        $oldarr=explode(',',$oldarrstr);
        $newarr=array_unique(array_diff( $oldarr,$arr));
        return  implode(",",$newarr);
}