The problem of header implementation file download

You need to click the button to get the information and download the content in the form of a file.
But now clicking the button opens a new window and displays the content instead of popping up a download window.
The code is as follows:

<code>$filename = $this->input->cookie('merchant_id');
$timestamp = date("YmdHis",time());
$filename .= $timestamp.'.'.$fileType;

$title = mb_convert_encoding($title,'gbk','utf-8');

header('Content-type: application/octet-stream');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Content-Disposition: attachment; filename=' . $filename);
echo $title;

$ret = $this->download_model->QueryList($Req, $Resp);
$content = $this->GetDownLoadContentNew($ret['bill_list'], $fileType);
echo $content;
</code>

GetDownLoadContentNew formats the content accordingly.
Don’t know what’s wrong or haven’t noticed something? I hope you can help me take a look, thank you. (The fileType is csv or txt, which is the same on different browsers but cannot trigger the download)

Reply content:

You need to click the button to get the information and download the content as a file.
But now clicking the button opens a new window and displays the content instead of popping up a download window.
The code is as follows:

<code>$filename = $this->input->cookie('merchant_id');
$timestamp = date("YmdHis",time());
$filename .= $timestamp.'.'.$fileType;

$title = mb_convert_encoding($title,'gbk','utf-8');

header('Content-type: application/octet-stream');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Content-Disposition: attachment; filename=' . $filename);
echo $title;

$ret = $this->download_model->QueryList($Req, $Resp);
$content = $this->GetDownLoadContentNew($ret['bill_list'], $fileType);
echo $content;
</code>

GetDownLoadContentNew formats the content accordingly.
Don’t know what’s wrong or haven’t noticed something? I hope you can help me take a look, thank you. (The fileType is csv or txt, which is the same on different browsers but cannot trigger the download)

<code>/**
  * 强制下载文件 
  * @param string $file 文件路径 
*/
function force_download($file){ 
    if ((isset($file)) && (file_exists($file))) {
        header("Content-length: ".filesize($file)); 
        header('Content-Type: application/octet-stream');
        header('Content-Disposition: attachment;filename="'.basename($file).'"'); 
        readfile($file); } 
    else { 
        echo "No file selected"; 
    }
}
//使用示例
force_download('./test.jpg');</code>