分批次从musql取数据，每次取1000条

$t = new Gettags();

$num=$t->sum_tag();
$num=$num/1000;
$flag_num=ceil($num);

$flag_array=array();

$f=0;

for ($i=1; $i<=$flag_num; $i++) {

    $tag_name=$t->get_tag($flag);
    foreach($tag_name as $k=>$v){
        $flag_array[$f]=$v;
        ++$f;
    }

}

    //查询标签库所有标签

    public function get_tag($n){

        $n=$n*1000;
        $m=$n+999;
        $sql="select tag_name,tag_id from xcar_tag where status >0 limit $n,$m";
        $res = $this->tdb->query($sql);
        $result = $this->tdb->fetch_array($res);

        return $result;
    }

    //计算标签库
    public function sum_tag(){

        $sql="select count(tag_id) as count from xcar_tag where status >0";

        $query  = $this->tdb->query($sql);
        $result = mysql_fetch_array($query);

        return $result['count'];

    }