php导出excel 大数据 时候需要注意的问题

 /**
     * 构造函数
     */
    function __construct(){
        parent::__construct();
        $this->check_page();
        $this->control   = "admin-2016-yyyl3";
        $this->arr_table = array(
            1 => "yyyl_order"
        );
       load_config("admin/onload");
        load_model("admin/common");
        $this->model = new CommonModel("dmz_act_2016");
    }

//导出excel

    public function saveCSV(){
        header("Content-type:text/html;charset=utf-8");
        ini_set("display_errors", "Off");
         ini_set("max_execution_time", "3000");                                        // 就是这里需要手动改变下php.ini中的运存的大小和超时时间的长短
         ini_set("memory_limit", "1024M");
        error_reporting(0);
        $t = (int) $_GET["t"];
        if($t == 3){
            $con = mysql_connect("10.21.2.192", "game", "game");
            mysql_select_db("dmz_act_basic_2016", $con);
            $sql = "set names utf8";
            mysql_query($sql);
            $search_where = " select * from yyyl_order";
            $ret_mysql    = mysql_query($search_where);
            $ret          = array();
            while($row = mysql_fetch_array($ret_mysql)){
                $arr_item             = array();
                $arr_item["account"]  = $row["account"];
                $arr_item["uin"]      = $row["uin"];
                $arr_item["zone_id"]  = $row["zone_id"];
                $arr_item["username"] = $row["username"];
                $arr_item["age"]      = $row["age"];
                $arr_item["sex"]      = $row["sex"];
                $arr_item["email"]    = $row["email"];
                $arr_item["phone"]    = $row["phone"];
                $arr_item["qq"]       = $row["qq"];
                $arr_item["model"]    = $row["model"];
                $ret[]                = $arr_item;
                //var_dump("ddd");
            }
            $header = array(
                "account"  => "账号",
                "uin"      => "UIN",
                "zone_id"  => "大区ID",
                "username" => "昵称",
                "age"      => "年龄",
                "sex"      => "性别",
                "email"    => "邮箱",
                "phone"    => "手机号",
                "qq"       => "QQ",
                "model"    => "机型"
            );
            $data   = array_merge($headers = array($header), $ret);
            load_library("php-excel");         //  加载phpexcel库
            $xls = new Excel_XML("UTF-8", false, "预约有礼" . $t);
            $xls->addArray($data);
            ob_flush();
            flush();
            $xls->generateXML("jzsn-" . date("YmdHis"));
            exit();
        }
        $where   = "where table_name=yyyl_order";
        $rows    = $this->model->get_list("Information_schema.columns", $where, "column_name,column_comment");
        $headers = array();
        foreach($rows as $row){
            if($row["column_name"] = "prize_id"){
                $view1["fields"][$row["column_name"]] = "奖品序号";
            }
            $header[] = !empty($row["column_comment"]) ? $row["column_comment"] : $row["column_name"];
        }

        $where  = "";
        $fields = "*";
        if($t == 4 && isset($_GET["num"])){
            $prize_type = (int) $_GET["num"];
            $where      = "where prize_type = $prize_type";
        }
        $rows = $this->model->get_list($this->arr_table[$t], $where, $fields);
        $data = array_merge($headers = array($header), $rows);
        load_library("php-excel");
        $xls = new Excel_XML("UTF-8", false, "预约有礼" . $t);
        $xls->addArray($data);
        ob_flush();
        flush();
        $xls->generateXML("jzsn-" . date("YmdHis"));
        exit();
    }