PHP QR code generation and download implementation

<?php
 
//Introduce phpqrcode library filedefine('IN_ECS', true);
 
require(dirname(__FILE__) . '/includes/');
include('includes/');
 
// QR code data$data = '';
$filename = 'shopEwm/'.'';
 
//down_file('',BASE_PATH);
setShopEwm($data,$filename);
 
//Generate QR code picturesfunction setShopEwm($data,$filename){
// Error correction level: L, M, Q, H 
  $errorCorrectionLevel = 'L';
  // Point size: 1 to 10  $matrixPointSize = 4;
  //Create a QR code file  QRcode::png($data, $filename, $errorCorrectionLevel, $matrixPointSize, 2);
  //Enter the QR code to the browser  //QRcode::png($data);
}
//Download QR code picturefunction down_file($file_name){
  $file_sub_dir = str_replace('\\','/',realpath(dirname(__FILE__).'/'))."/shopEwm/";
  //Reason: PHP file function is relatively old and requires Chinese transcoding gb2312  $file_name=iconv("utf-8","gb2312",$file_name);
 
  //Absolute path  $file_path=$file_sub_dir.$file_name;
  //1.Open the file  if(!file_exists($file_path)){
    echo "The file does not exist!";
    return ;
  }
 
  $fp=fopen($file_path,"r");
  //2. Process the file  //Get the size of the downloaded file  $file_size=filesize($file_path);
 
  /* if($file_size>30){
 
   echo "<script language='javascript'>('too large')</script>";
   return ;
   } */
 
  //Returned file  header("Content-type: application/octet-stream");
  //Return according to byte size  header("Accept-Ranges: bytes");
  //Return file size  header("Accept-Length: $file_size");
  //The pop-up dialog box of the client here, the corresponding file name  header("Content-Disposition: attachment; filename=".$file_name);
 
  //Release data to the client 
  $buffer=1024;
  //For the sake of download security, we'd better make a file byte read counter  $file_count=0;
  //This sentence is used to determine whether the file is over or not  while(!feof($fp) &amp;&amp; ($file_size-$file_count&gt;0) ){
    $file_data=fread($fp,$buffer);
    // Statistics how many bytes have been read    $file_count+=$buffer;
    //Send some data back to the browser;    echo $file_data;
  }
 
  //Close the file  fclose($fp);
 
}