前台HTML：

添加download属性，不打开download.php页面

<a style='color:blue' href='download.php' download='data/CrawlerID.txt' target=_blank>下载</a>

download.php

1：从数据库中导出内容

2：fread输出到页面

<?php
    //下载数据
    header('Content-Type:text/html;charset=utf-8');
    $crawlId=$_GET['id'];
    
    //导出sql语句：Select pid,price Into OutFile 'F:/QQPCmgr/Desktop/Data_OutFile.txt' fields terminated by ',' From `t_product`
    //导出文件命名格式Crawl_ID_txt;
    $filePath = "D:/WWW/amazon_crawl_system/data/";//此处给出你下载的文件在服务器的什么地方
    $fileName = "CrawlerID_".$crawlId.".txt";
    
    //删除文件
    if(file_exists($filePath.$fileName)){
        unlink($filePath.$fileName);
    }
    
    include_once('./mysql.php');
    $conndb=new ConnDB();
    $conndb->connect("127.0.0.1","root","root","amazon");
    
    //首先从t_crawl_url表中获取对应的id值，拼接sql语句
    $sql="select id from t_crawl_url where crawl_id=".$crawlId;
    $request=$conndb->queryarr($sql);
    $str='';
    if($request){
        foreach($request as $key => $values){
            $str.="crawl_url_id='".$values['id']."' or ";
        }
        $str=substr($str,0,strlen($str)-4);
        //echo $str;
    }else{
        echo "error";
        exit;
    }
    
    $sql="select pid,price Into OutFile '".$filePath.$fileName."' fields terminated by ',' lines terminated by '\r\n' From `t_product` where ".$str;
    
    $request=$conndb->query($sql);
    if($request){
        /*echo "<script> window.location.href='download.php?id=".$crawlId."&file=".$saveFile."';</script>";*/
    }else{
        echo "<script> alert('下载失败');</script>";
        exit;
    }
    
    //此处给出你下载的文件名
    $file = fopen($filePath.$fileName, "r"); //打开文件
    //输入文件标签
    header("Content-type:application/octet-stream ");
    header("Accept-Ranges:bytes ");
    header("Accept-Length:   " . filesize($filePath.$fileName));
    header("Content-Disposition:   attachment;   filename= ".$fileName);
    
    //输出文件内容
    echo fread($file, filesize($filePath . $fileName));
    fclose($file);
    

?>