How to download files from WeChat applet through back-end PHP

Scenario: The WeChat applet calls the wx.downloadFile() API to download a file, and the PHP backend performs processing and returns the file process;
Process:
1. The applet displays a list of files that need to be downloaded;
2. Click download and request the PHP interface, carrying a parameter for the name of the file you want to download;
3. Receive the parameter in PHP, and then search the folder to see if there is the file;
4. Find file and return the file to the applet;
5. The applet saves the file returned by the backend, click to open the file, and preview the code:
wxml

<view>文件列表</view>
<view wx:for=&#39;{{search_store}}&#39; wx:key=&#39;{{index}}&#39;>
  <view bindtap=&#39;dom&#39; id=&#39;{{index}}&#39;>文件名：{{item.fileName}} 点击下载</view>
</view>

js

  dom: function (e) {
    var index = e.currentTarget.id;
    var data = this.data.search_store[index].fileName
    var that = this;
    wx.downloadFile({
      url: 'https://dwb.lynncain.cn/H5/dom.php?str=' + data, //下载路径携带 参数=文件名
      success: function (res) {
        console.log(res.tempFilePath)
        wx.saveFile({ //下载成功后保存
          tempFilePath: res.tempFilePath,
          success: function (res) {
           wx.showToast({
             title: '下载成功！',
           })
           wx.getSavedFileList({ //获取下载的文件列表保存到data
             success: function (rrr) {
               console.log(rrr.fileList)
               that.setData({
                 fileList: rrr.fileList
               })
             }
           })
          }
        })
      }
    })
  },

php

<?php
    header("Access-Control-Allow-Origin: *"); //解决跨域
    header(&#39;Access-Control-Allow-Methods:GET&#39;);// 响应类型  
    header(&#39;Access-Control-Allow-Headers:*&#39;); // 响应头设置 
    $link=mysql_connect("localhost","root","root"); 
    mysql_select_db("new_test", $link); //选择数据库
    mysql_query("SET NAMES utf8");//解决中文乱码问题
error_reporting(0);
$str = $_GET[&#39;str&#39;];
$file_path="upload/".$str;
if (! file_exists ( $file_path )) {    
header(&#39;HTTP/1.1 404 NOT FOUND&#39;);  
} else {    
//以只读和二进制模式打开文件   
$file = fopen ( $file_path, "rb" ); 
//告诉浏览器这是一个文件流格式的文件    
Header ( "Content-type: application/octet-stream" ); 
//请求范围的度量单位  
Header ( "Accept-Ranges: bytes" );  
//Content-Length是指定包含于请求或响应中数据的字节长度    
Header ( "Accept-Length: " . filesize ( $file_path ) );  
//用来告诉浏览器，文件是可以当做附件被下载，下载后的文件名称为$file_name该变量的值。
Header ( "Content-Disposition: attachment; filename=" . $str );    
//读取文件内容并直接输出到浏览器    
echo fread ( $file, filesize ( $file_path ) );    
fclose ( $file );    
exit ();    
}    
?>

This article introduces how to download files from WeChat applet and process them through back-end PHP. For more related knowledge, please pay attention to the php Chinese website.

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