<?php

 set_time_limit(0);

 ini_set('memory_limit', '128M');

 $fileName = date('YmdHis', time());

 header('Content-Encoding: UTF-8');

 header("Content-type:application/vnd.ms-excel;charset=UTF-8");

 header('Content-Disposition: attachment;filename="' . $fileName . '.csv"');

 //打开php标准输出流

 //以写入追加的方式打开

 $fp = fopen('php://output', 'a');

 //连接数据库

 $dbhost = '127.0.0.1';

 $dbuser = 'root';

 $dbpwd = '';

 $con = mysqli_connect($dbhost, $dbuser, $dbpwd);

 if (mysqli_connect_errno()) {

    die('connect error');

 }

 //选择数据库

 $database = 'test';

 mysqli_select_db($con, $database);

 //设置编码

 mysqli_query($con, "set names UTF8");

 //我们试着用fputcsv从数据库中导出1百万的数据

 //我们每次取1万条数据，分100步来执行

 //如果线上环境无法支持一次性读取1万条数据，可把$nums调小，$step相应增大。

 $step = 100;

 $nums = 10000;

 $where = ""; //筛选条件

 //设置标题

 $title = array('ID','姓名','年龄','性别');

 foreach($title as $key => $item) {

     $title[$key] =iconv("UTF-8", "GBK", $item);

 }

 //将标题写到标准输出中

 fputcsv($fp, $title);

 for($s = 1; $s <= $step; $s++) {

     $start = ($s - 1) * $nums;

     $result = mysqli_query($con,"SELECT * FROM `test` ".$where." ORDER BY `id` LIMIT {$start},{$nums}");

     if($result) {

         while($row = mysqli_fetch_assoc($result)) {

             foreach($row as $key => $item) {

                 //这里必须转码，不然会乱码

                 $row[$key] = iconv("UTF-8", "GBK", $item);

             }

             fputcsv($fp, $row);

         }

         mysqli_free_result($result); //释放结果集资源

         //每1万条数据就刷新缓冲区

         ob_flush();

         flush();

     }

 }

 //断开连接

 mysqli_close($con);